priming before riveting

Priming inside surfaces that will be riveted is the focus of this question.

As the third owner of my particular kit there are lots of scratches on the skins that concern me enough to want a little more protection than if it were a clean out of the box skin. While most appear small enough to sand out easily a few are a little deeper. Not enough to worry about skin strength but enough to worry that the Alclad is compromised.

I live in the Chicago far north suburbs so normally not a "salt environment" but once flying I plan to try (emphasis on "try") to follow Rosie's lead and travel to the coasts and other places as much as I can. Why build an RV and stay in Chicago?

I want to prime as if I were say, on the Gulf or East Coasts, and want to use a system that will allow me to prime in the basement (it is Winter up here for at least another 4 months) and if possible have a primer that does not require a top coat.

I know this will generate some lively discussion and has in the past been beaten to death but with new products like Prekote, AFS and others I think it bears some current thinking and would like to hear the latest thoughts on what is best to use in this type application.

Again for this discussion I am speaking only of the inside surfaces not the exterior or finished cockpt area.

I have some DX1791 from my RV9A project that got sold but it is about 3-4 years old and alhough unopened I think it is safe to say it is past it's shelf like.

My previous business was a paint and collision shop (27 years) and while I don't want to come across as a "pro", you might imagine that paint issues of all kinds hold some interest to me and I do have some background knowledge on the subject.

That said; the PPG DX1791 is a great product (I used PPG products for over 20 of those years) for the purpose as you describe (inside surfaces not intended to be painted) and I was originally intending to use that myself. And for those who already have it, there is absolutely no reason to change if you're already using it.

However, I did some research on the Sanchem products, and even spent some time on the phone with a rep, and have decided to go with the Sanchem SafeGard 6100 (parts A,B, and C... C is a precleaner and B/C is the two part mix applied after the C cleaning).
Unless I've been grossly "oversold", it appears that the Sanchem 6100 offers protection beyond that of the DX1791 by itself (which was always intended as designed to be top coated).
The 6100 does not need a topcoat, but you can even go further with interior protection by coating it with the Sanchem 3400 Seal#2.

The 6100 is not even that expensive, being about $30 per gal. (each) for the A & B, and $35 for a gallon of the C cleaner. Plus, it works better if it's wiped on rather than sprayed so overspray isn't an issue.
I've got my order on the way, and you might find it worth a look.
The 6100 should also be a great conversion coating for the outside surfaces as well, and all that's needed after applying it is to spray a sealer coat of primer (preferably DP40/401) and then go right into the Deltron, Delthane, or whatever Urethane type finish you want. A finish like that will outlast the airplane (or at least, you )
By the way, Precote didn't come out too well in comparison tests done for the Military.
Also by the way, according to the Sanchem rep, the 6100 does NOT have a shelf life even after it's been opened (but keep the lid tight). However, the mixed A&B parts DO have a chemical life of 12 hours... once mixed, you need to use it up within 12 hours or throw it away.

www.sanchem.com

Vern

thanks Vern

Lots of good information. That's what I'm looking for.

My biggest concern with the DX1791 besides being beyond shelf life is the need for the topcoat. If it offers no corrosion protection why put it on?

How much is enough?

What I don't know, having not been exposed to too many aircraft in my few years of flying so far, is how much of a problem is corrosion of aluminum?

Hypothetically, what would happen if you didn't prime anything internal on the airframe? I realize that location makes a big difference, so lets assume it's what I would think is typical (or maybe average) for an RV... Mid-west weather, hangar kept. Is it gonna fall apart in 20 years? Or is what Sam Buchanan said closer to the truth?

And how much additional time and pain is it really to prime all those parts?

My opinion (note that I said "opinion" so no flames here) is that our RV's will outlive 99% of the builders without any inside surface protection whatsoever on the inside. Alclad is a very durable material against corrosion and the only reason I personally am going to do some protection inside is because of the occasional scratching I'm sure will happen.

The DX1791 does offer "some" corrosion protection, and it's actually at least as good as most of the other options people have talked about. It's at least as good as the Veriprime that (I believe) is used on the inside of the Quickbuild kits.
The problem is that virtually ALL the other products mentioned and used by various builders are also designed to be top coated so a product being one of the best in that category is still not a perfect product unless it's topcoated.

That's why I like the (claims) made by Sanchem about the 6100 product I mentioned in the earlier post. It is NOT a primer nor sealer; it is a "conversion" coating and does not depend on a film build to do what it does. It is a true conversion product that protects the aluminum without having to be top coated.
Also, because it's not a coating per se, it adds virtually no weight at all unless you decide to follow it with a top coat (but again, there is no need; Sanchem is very clear about making the "no topcoat needed" claim which PPG, Dupont, and the rest do not with any of their products).
The Sanchem 6100 itself is as thin as water and gently wiping it over the prepared surface is all you need to do. If the surface then changes color to the brownish gold color, you KNOW it has performed it's chemical function and you're done. If it doesn't change color, then you know that the precleaning with the Part C product wasn't done well enough and would have to be repeated.
The process for using the 6100 is also much easier than other methods of preparation for most other products as well. All you do is to scrub down the bare panel with a ScotchBrite pad with the 6100 Part C, and then wipe on the mixed Parts A/B of the 6100. That's it; no sloshy alodine mess, no rinsing, no spraying. Just wipe it on, watch it turn color, let it dry, then pound some rivets.

I'm pretty excited to work with the SafeGard 6100 because it's the first product I've come across that does EXACTLY what we want to do with regard to protecting the inside surfaces of the aircraft without needing a top coat or adding any weight or requiring a bunch of messy preprep steps.
Of course, I'm afraid I've got the QuickBuild kit and the inside has already been primed by the Phillipine assembly people with something else (it looks like Veraprime to me). But I'll be using the Sanchem 6100 on all the rest of the metal just for grins.

Vern
RV7-A

Vern, what do you think would happen if you wiped some SafeGuard 6100 over aluminum that has the Veriprime on it? A big mess or more corrosion-proofing? It might be a good thing to test on scrap. I would interested in knowing.

That would be a waste of time because the 6100 acts directly (chemically) on the aluminum.
Keep in mind that the 6100 is not a "coating" like a primer or sealer, but is a material that causes a chemical process to take place in the aluminum itself so using it over any kind of existing barrier that covers the aluminum would have no effect.
You'd need to clean off every bit of the Veriprime and get to clean, bare aluminum before using the 6100 3 part system.

However, I still have the opinion that we do not "have" to protect the inside surfaces as much as we do considering that we are, after all, working with Alclad material. (Keep in mind I'm only referring to the aluminum here, not the steel which MUST be carefully treated for long term rust prevention and the 6100 is intended only for aluminum... other metals require a different system).
You would likely do more harm than good if you were to go through the work of stripping off all the Veriprime already on the panels.

The entire inside of my QB RV7-A has been primed already, and I'm not 100% sure with what. But I trust that Van's did some basic homework on the subject before specifying the material and I'm not going to lose any sleep over it. Especially since it saved me an untold number of months (years?) by building the QB parts for me. I will, however, go with the 6100 everywhere else I want to treat aluminum.

So if you have already used one of the several methods of protection that have been talked about in connection with building RV's, I'd just leave it alone. Like they said in the movie, "Build it, and it will fly". Or something like that.

Vern
RV7-A

Why prime interior surfaces at all? Really, what benefit do you expect to derive from countless hours and hours of prep and priming?

Again, if you live in a salt envirnment, then there's a case to be made for priming. If the parts are not ALCLAD, then they should be primed. If not, it is a waste of time, money, weight, and building momentum that most builders can ill afford. What you gain is some peace of mind and questionable corrosion protection since most builders don't apply primer they way the manufacturer specifies for maximum corrosion protection anyway.

Look inside the wing of a 1960's Cessna or Piper. What you'll see is bare aluminum. Even if your airplane, after being parked in a hangar its whole life, and never seeing bad weather, and after receiving tender loving care from the builder/owner, just happens to get a little corrosion, you can always fog the inside surfaces with corrosion inhibitor 20 years from now.

f1rocket said:

Why prime interior surfaces at all? Really, what benefit do you expect to derive from countless hours and hours of prep and priming?

Again, if you live in a salt envirnment, then there's a case to be made for priming. If the parts are not ALCLAD, then they should be primed. If not, it is a waste of time, money, weight, and building momentum that most builders can ill afford.

Click to expand...

Well yea, but just putting the airplane together without all that extra work is way to easy.

I know the admonition about needing to prime only if the aircraft is kept on a sea coast, but I'll bet that all RV builders have the idea that they will at least be traveling to the coasts so maybe that's why there's so much concern.

While I don't technically live on the water, I am in Houston which is close enough for me to want to do something a little more than just leaving the Alclad bare.

Vern
RV7-A

I don't fault anyone who chooses to prime. Heck, I primed the holy heck out of my RV-6. Probably added 10 lbs to the gross weight!

I've been amazed at how much faster things go together if I don't have to stop and break out the priming gear.

is this a good compromise?

Based on Vern's comments of how easy the Sanchem sounds to apply in that you simply wipe it on and it offers at that point more corrosion protection than not priming at all and possibly more than Variprime et al but is not as difficult, smelly, costly or most importantly..time consuming doesn't it sound like the possible middle ground I was looking for?

It is beginning to look that way to me.

Simply wiping off or (down) all the parts before riveting sounds like something we already do so if the rag we use has a conversion chemical that offers some basic protection while only delaying riveting by a few minutes while it dries it doesn't sound like a bad thing. It certainly solves the problem of finding or making a spray booth, figuring how to prime and dispose of and clean things while living on well water with all the minerals and sodium (water softener salt) that could and probably would affect the aluminum.

This is getting somewhere.

Randy, great ideas too. Isn't it funny how we say we don't need to do things but then we do them anyway?

jimpappas said:

Randy, great ideas too. Isn't it funny how we say we don't need to do things but then we do them anyway?

Click to expand...

There's quite a bit of my Rocket that is not primed. None of the empennage skins, wing skins, or fuselage skins are primed, and for the most part, only parts of the skeleton. Anywhere there's angle, I primed because they're raw aluminum. The interior is primed because it's topcoated.

Next airplane will be entirely shiney, inside and out!

jimpappas said:

Sanchem ... offers at that point more corrosion protection than not priming at all and possibly more than Variprime et al but is not as difficult, smelly, costly or most importantly..time consuming doesn't it sound like the possible middle ground I was looking for?

Click to expand...

That's exactly why I'm so impressed with the Sanchem. If I had to choose between cleaning/scrubbing/alodine/rinsing/priming ad infinitum and that was my only choice, I can assure you that I would be quite happy with just shiny bright Alclad all over the place.

But the simplicity of prepping for, and then applying the Sanchem, coupled with what seems to be it's better effectiveness for the purpose than the usual primers, means that it really should be the middle ground we're all hoping for.
For those who are the retentive type, they can go the extra (but unnecessary) step of following the 6100 with the 3400 Seal#2. If I were to go that far, however, I'm pretty sure that I would want to add a clause to my will that I be buried in my RV... sitting in the left seat with my head phones on.

Vern
RV7-A

Vern,

The Sanchem site doesn't give much info on the 6100 product, but what is there seems to indicate that it is more of an alternative to Alodine rather than a "true" primer. I'm not sure it would be a replacement for an epoxy primer for those who wish to go that way, but it might be a less toxic method of providing Alodine-like surface conversion. Dis the Sanchem rep give you any additional info beyond that which is online?

Paul Trotter
RV-8 82080

I spent about 20 minutes on the phone with the rep asking questions about which product would fit my intent. After giving him a very detailed explanation about what I was doing and what I wanted to end up with as far as protection, he without hesitation said the 6100 was exactly what I was looking for. He noted that the 6100 is exactly the same as the 7000 but that the 6100 accelerates the chemical conversion and is "faster" to use.

You're right that the Sanchem site isn't very clear with information about the products other than a general way, and that's why the personal phonecon was helpful.

You're correct in making the comparison between Alodine and the 6100 rather than comparing the 6100 to epoxy primer. That's because, like Alodine, the 6100 is not a "coating", but rather, is a chemical conversion process that reacts directly with the aluminum. Epoxy primer is just that, a primer, and it's benefit is that epoxy primer does a good job of inhibiting corrosion when applied correctly, but it does not actually react with the aluminum.
And because the 6100 is not a primer, it adds negligable weight (if any) while the epoxy primer is chocked full of "solids" that does add weight (but only a few pounds).

The rep seemed to be quite confident that the 6100 far surpasses the protection offered by Alodine but we didn't get into the specific discussion of the chemistry involved.
The one thing that caught my attention is that the rep was VERY clear about the fact that the 6100 does NOT have to be top coated with ANYTHING for it to be very effective for long term protection.
If you read any of the P-sheets for Alodine, you will see that they always call for following up with an approved primer (usually within 4 hours).

For someone who was leaning toward going with epoxy primer such as the PPG DP/DF series, it looks to me that using the 6100 followed up with the Sanchem 3400 Seal#2 would not only be a lot easier, but probably better protection as well because you're dealing with a true chemical conversion process protected on top by the sealer rather than just a (very good) primer.

An interesting note about the 3400 Seal#2 is how it's applied: What you do is to spray it on top of the 6100 and it will be white. Then, and this is mandatory, you wave a heat gun over it as you go and you know it's "done" when it changes color. You only have to get it to 200 degrees which is easy with any heat gun and the heat caused crosslink is immediate as soon as the temp is reached.
Even after describing all that and how much more the 3400Seal#2 adds for long term protection, the rep still said that I really didn't need to go any further for my described purpose than just the 6100.

Let's all stay real here and step back to say again that most of us really don't need to prime at all. I just like the 6100 (only) route because it's just too darn easy and you get a lot for it.

Vern
RV7-A

Vern,

That is very interesting. I wish Sanchem had more info on the 6100 product on their site. I guess I will give them a call. Do you recall who you talked to?

While I am going through the complete Alumprep/Alodine/Epoxy Primer process on the inside of my emp and wings where I cannot see inside well to inspect, I am considering not doing this on the fuse where I can keep an eye on things easier. This might be a good alternative.

Sanchem's comparison info on their site for their other products seems to indicate that Alodine is a little better. I assume that from your discussions with them that they feel the 6100 product is better than their other products in comparison to alodine.

BTW, Henkel's Tech notes on Alodine don't seem to state that overcoating is require, only that if it is overcoated, it shold be done soon afterward. Where did you read this info?


Thanks for the info,

Paul

Paul,
Try John Flicher at 1-800-621-1603. Called him yesterday after reading Vern's 1st post and had pretty much the same conversation with him that he did. Their 6100 system sounds the way to go.

Todd Stovall

I just had a long conversation with John Flicher at Sanchem and their product sounds like it could be a very good compromise between no priming and a full epoxy primer. It might meet the needs of those who really don't want to prime, but want a bit more protection than alclad. Since it is a surface conversion rather than a paint, it does not add any measurable weight. Also, it is non-toxic which makes it much more desirable to use than alodine.

I ordered some of the 6100 product and will give it a test and report back.

Paul Trotter
RV-8 82080

Paul,
After many years decifering paint product descriptions, P-sheets, and MSDS sheets, I have learned to read them a little differently than most people might. I had to because if a product isn't used properly, then the company wouldn't offer any help to fix a problem. In the case of the Alodine by Henkel, a careful reading of their P-sheet shows that the Alodine is only PART of a TOTAL system meaning that a topcoat of paint is expected, by Henkel, to be part of that total system.

Here's the P-sheet, http://www.loctiteaero.com/Images/Datasheet_PDF/hst_alodine1201.pdf and directly from it comes these little gems that you have to know how to interpret:

This chrome conversion coating offers the best
affordable substrate for both paint adhesion and corrosion resistance.
The key words here are "substrate" (meaning "foundation") and for "paint adhesion". Both terms tell you directly that the Alodine is designed to be used under something (hence; "substrate"), and that it's designed to be used to promote "paint adhesion" (meaning that it is designed for paint to be sprayed on top of it in order to form a complete "system").

The work, after processing and drying, is ready to be painted.
This is the last line of the "Process" description and is a direct statement that Henkel expects that the treated metal WILL be painted as part of the total process.

Powdering of a chrome conversion coating can result from poor cleaning,
over reacting, or for other reasons. Powder can affect paint
adhesion.
This is a simple description of a possible application problem (to be avoided), but again, associated with a clear reference to "paint adhesion" which tells you again that Henkel expects their Alodine product to be top coated.

Blistering problems under paint are often the results of poor rinsing.
Again, what can happen "under paint" shows that Henkel expects that paint is going to part of the "total" process which only includes Alodine treatment.

Nowhere in the Henkel P-sheet is there any reference that suggests that the Alodine does NOT need to be coated.
On the other hand, there is a direct statement by Sanchem that the 6100 does NOT have to be top coated with ANYTHING in order for it to offer it's designed protection.

And yes, it was John Fletcher whom I talked to about what he thought would be the best material of what they offer for treating the inside of the aluminum while building.

Vern
RV7-A

Vern,

This is an interesting discussion.

I agree that there can be multiple interpretations of P-sheets, etc. and that one sometimes has to read between the lines. One can also do this with the Sanchem info. Specifically, they state that "Sanchem's Chrome-Free Safegard CC gives you the paint adhesion and the corrosion resistance of chromate based conversion coatings without the association health and disposal costs." This tends to indicate that overcoating may be desirable. Just nitpicking here

I think the important to determine is what any products "designed protection" actually is and how that relates to our individual goals in using a product. You mentioned Sanchem states that it does not need to be overcoated to provide its "designed protection". This may be so, but what is that designed protection"? My understanding of Sanchem's designed protection from reading the info and talking with them, is that its designed protection is pretty much the same as alodine's designed protection. Their own MIL-Spec tests show that without overcoating with their own Seal #2 that their corrosion protection is slightly less than that of alodine, particularly on 2024-T3. It still meets the MIL-Spec, but the difference is measurable.

They way I read this info, and also what I got out of my discussion with John Fletcher, is that they feel that their product is basically a safer version of alodine, providing roughly eqivalent protection without the toxicity of chrome. The 6100 product, as well as their other aluminum products, is an oxide conversion rather than a chromate conversion, but still a surface conversion and not a true primer.

John noted that these tests were done before they developed their Seal #2 product and that when the Seal #2 is applied over the 6100, that the protection exceeds that of alodine.

When I mentioned the slightly poorer test results, John's response was "It still meets MIL-Spec, so which would you rather use? toxic alodine or non-toxic Sanchem?" This makes the product attractive, but leads me to believe that its protection is equivilent to alodine.

All this being said, if one wants the corrosion protection of alodine, the Sanchem product is probably a preferrable solution due to the lack of toxicicity. However, if one does not feel that alodine alone is sufficient, then 6100 will probably not be sufficient either, or perhaps might be when overcoated with their Seal #2. But, this might be a great product for those who would otherwise choose not to prime, since it is easy to apply, non-toxic, and will add a level of protection they would not otherwise have. It also may be a good alternative to alodine for those who want to prime over it.

I did find it interesting enough to order some, including the Seal #2, and will test it. I will probably continue with my alodine and epoxy primer on the inside surfaces of my wings (since I'm almost done) where inspection is difficult, but may switch to the 6100 on the inside of my fuse where I can see things better. (I also like the looks of the green primer)

Unfortunately we don't have a track record of this product for our use and it is difficult for individuals such as ourselves to perform really in depth, or long term, testing, so we may have to wait awhile to see the real results.

In any case, any product that makes things easier, or safer, is worth investigating and this looks like a potential winner. Let's continue our tsting and see where it leads.

Paul

Keep in mind that as we pick the nits on this subject, it's really just a fun discussion more than being a truly "important" subject. Only the most retentive of us lose sleep over any of this because the absolute reality is that if we didn't do ANY of this, we would still end up with an aircraft protected against corrosion at least as well as any brand new GA aircraft due to the protective properties of Alclad by itself.
I'd be willing to bet that even an RV built on a salt water coast without any (additional) inside protection would last 30+ years before showing any significant corrosion. The only car that I own that's more than 30 years old is made of fiberglass, if you get my drift.

With that said, I can easily cut to the chase by making a simple observation. And that is that:
1. Bare Alclad is already more than we need for corrosion protection
2. Adding a conversion coating like Alodine or 6100 (and no more) is somewhat better
3. But getting right to the bottom line based on my experience, using a true conversion product like Alodine or Sanchem 6100, and then following up with an epoxy primer like the PPG DP/LF system is about as bullet proof as you can get.

If you're using both the Alodine AND following it with epoxy primer now, and you don't mind the work involved, and you don't mind the weight penalty of the epoxy primer (it's not much), then I wouldn't change a thing because what you're doing is the absolute highest degree of corrosion protection you can do.

Even if you were to go further and then paint on top of the epoxy primer with urethane paint, you wouldn't be adding any more protection than you already have because the epoxy primer will give you a "topcoat" protection once it's cured (I'm sayin this only with respect to the epoxy primer being used on an inside surface and not exposed to direct sun or the elements).
Note that this comment applies ONLY to catalyzed epoxy primers such as the PPG DP/LF 2-part system, and not to just anything that says "primer" on the label. Once catalyzed epoxy primer goes through it's crosslink (curing) phase, it is no longer porous like standard primers and gives protection (on inside surfaces) as good as any paint topcoat.

In the end, I like the 6100 because it is clearly the easiest to apply among all the conversion coatings (I've done my share of the Metalprep/Alumiprep/Alumigrip/Alodine mess in years past), and it's at least as good as any of them.
If I can get a warm, fuzzy, feel-good feeling about corrosion protection but don't have to work very hard to get it, I'm there.

My whole plan will be to do the 6100 on the entire remainder of any aluminum (except for painting the cockpit area). Then for an outside finish that will live even longer than the worms that will thrive on my long buried carcass, I'll be going with the 6100 as the conversion coat followed by the PPG DP/LF epoxy primer and then finish with one of the PPG Urethane products.

Vern
RV7-A

Vern,

You're right about these discussions being more fun than important. I completely agree with your observations. I generally tend to overdo things so I have opted for the full blown etch/alodine/prime method. Probably overkill and this may change as I go on.

Only 1 comment though. I believe (but I may be wrong) that some of the 2-part epoxy primers are designed to be overcoated to provide complete protection. They are purposely porous to provide good adhesion for the top coat which then seals everything. Some are designed primarily to provide better adhesion for topcoating and do not provide much, if any, corrosion protection. When not overcoating, one should choose a primer that both seals as well as provides corrosion protection.

I guess we've probably beat this topic to death but it was interesting.

Let me know how your 6100 goes.

Paul
RV8

Thanks for all the input guys.

This has been fun and very informative as I had hoped and nobody called anybody any names

After all the discussion I think I am going to try the Vern method and go with the Sanchem instead of the Alodine and later go with the more serious process on the exterior when I get there.

I just ordered 1 gallon each of all 4 parts. A, B, C, and the sealer. I am looking forward to the process. Well i should say I am looking forward to not having to Alondine/Epoxy Primer.

ptrotter said:

Vern,

Only 1 comment though. I believe (but I may be wrong) that some of the 2-part epoxy primers are designed to be overcoated to provide complete protection. They are purposely porous to provide good adhesion for the top coat which then seals everything.

I guess we've probably beat this topic to death but it was interesting.

Paul
RV8

Click to expand...

Aww, c'mon, this is one of those topics that won't be considered beaten to death until each individual atom of the topic is finally sucked in by a Black Hole.

The only thing I'd like to clarify is that ALL primers, no matter what their chemical make up, are intended to be used under a topcoat of some sort. That's what it means for a product to be called a "primer".
That goes for epoxy primers, of course, but the one significant difference is that epoxy primers have only a narrow "open" time during which the crosslink chemical process has not yet, well, linked (obviously, that's why there's a catalyst involved).

Until that happens, epoxy primer DOES retain it's porosity to encourage better paint adhesion, but there's even more to it than that.
In any paint product, you have two kinds of adhesion properties to deal with; chemical adhesion where the chemistry of the topcoat actually reacts and bonds chemically with the primer (that's the best kind), and then mechanical adhesion where the topcoat "grips" the properly cleaned and sanded primer.

While epoxy is still in it's uncured open stage, it remains both chemically receptive to whatever chemically compatable finish is put on top of it, and it also remains porous where it encourages mechanical adhesion to the paint as well.
After epoxy primer cures, what happens is that it becomes a really good barrier against most anything (almost as good a barrier as paint itself), including any paint you might want to put on top of it.

So what you get when an epoxy cures beyond it's open stage is an epoxy primer that becomes worthless for it's originally intended purpose as a substrate, but great as a protective barrier as long as it's not left to weather in the elements as an external coating.
Beyond this curing time (note the term "cure", not "dry"), it will no longer chemically bond with any topcoat and, to reiterate, the result is that the cured epoxy primer then becomes a very good "barrier" and you would find that any paint put on top of it would be prone to chipping and peeling even if you sanded it well (sanding would only improve mechanical adhesion, and that's not good enough for a long term, durable finish).

That's why if you let PPG DP/LF (as an example) sit for longer than a week and you THEN want to top coat it, you don't have to take it off, but you DO have to sand it thoroughly and then reseal it with another coat of itself before painting it.

The short story, as if I could ever tell a short story, is that there's more to the story, and that's why the discussion will never end.

Vern
RV7-A

I just ordered a gallon of each from Sanchem too.

Can't wait to use it. They were very helpful and it sounds really easy.

Will report on it after I get to use it. Since I live about 30 miles from the plant it should get here pretty quick.

Thanks again to all for the input and I'm sure the debate will continue.

Thanks to Doug too for providing a forum format that allows us to bring up a topic like this and within 3 days have almost 300 sets of eyes on it and this much info on what was an old topic for many.

Time to go pound some rivets!

OK Vern, I'll keep beating

It is facinating how new ideas propogate through our hobby so fast due to forums like this one. The Sanchem 6100 prodcut was first mentioned by Vern on Monday and already 4 or 5 people have ordered it. It is also interesting that this is a completely new market for Sanchem. When I spoke to John Fletcher yesterday, he mentioned that he had never heard of individuals building airplanes until earlier this week when one of us called him. He now has a new market. I pointed him to the EAA website as well as to Van's so that he could get an understanding of what we do. Maybe we'll see them at a future AirVenture.

Vern, thanks for sharing all of your knowledge and experience, It never ceases to amaze me how much one can learn just by following these forums.

Paul
RV-8

ptrotter said:

OK Vern, I'll keep beating

When I spoke to John Fletcher yesterday, he mentioned that he had never heard of individuals building airplanes until earlier this week when one of us called him. He now has a new market.

Click to expand...

Wait a minute. You mean this empennage thing I ordered is part of an airplane? People can actually build like a real airplane that flies? Oh man, wait til the wife finds out...

Guys,
I'm interested in something that could be used over a completed wing. We will be getting our QB wings and fuselage soon, and I wanted to do something to promote adhesion after the outside surfaces have been cleaned up from the oily stuff they use for shipping the parts back to the states from the Phillipines.

It is my understanding that alodine cannot be used to treat the riveted outside surfaces, correct?? Obviously one would not use the Alumiprep for sure, picture the acid running into the rivet dimples and soaking into the rivet crevices!!! Yikes!

Well, what about this Sanchem stuff. Can it be used on the wings after they are built?? I will be using Super Koropon epoxy primer before topcoating, but I want to promote adhesion to this previously oily surface if possible.

Thanks,
Pete

Mustang said:

Guys,
I'm interested in something that could be used over a completed wing. We will be getting our QB wings and fuselage soon, and I wanted to do something to promote adhesion after the outside surfaces have been cleaned up from the oily stuff they use for shipping the parts back to the states from the Phillipines.

It is my understanding that alodine cannot be used to treat the riveted outside surfaces, correct?? Obviously one would not use the Alumiprep for sure, picture the acid running into the rivet dimples and soaking into the rivet crevices!!! Yikes!

Well, what about this Sanchem stuff. Can it be used on the wings after they are built?? I will be using Super Koropon epoxy primer before topcoating, but I want to promote adhesion to this previously oily surface if possible.

Thanks,
Pete

Click to expand...

It's best if you don't touch the outside surfaces with any chemical or primer until you're ready to paint; period. You gain nothing and only make more work for yourself later when it IS time to paint.
While you are building, lot's of people will come by to visit you and touch and feel and drool over the airplane parts ("Build it, and they will come"), and you yourself will be handling and crawling over (and drooling on ) parts of it as well.
None of that will hurt anything and will all come off when you start cleaning and prepping the surface metal for the paint process that will come many, many, many (did I say many?) months down the road.

I agree about the sloshy mess when doing the Metalprep/Alodine procedure. During all those years while I was in the business, I never did like the idea of how the various liquids could wick into hidden places.
Part of the process involves really thorough cleaning that requires physically wiping or Scotchbriting areas before and during the procedure, and there are simply some areas you can't physically get to. It is just those hidden areas where corrosion is most likely to develop. And you are very astute to note that the pre-treatment, acidic chemicals that will CAUSE corrosion, can get into places that make it difficult to properly flush out.
Still, that's basically how it's done which is why I've always looked for a better way.
But I digress...

You're getting way ahead of the game by even talking about painting since you don't yet have your QB parts yet, but just to give you something to obsess about (like many do with regard to this subject ), I'll throw some stuff at you:

My opinion, and this is just my opinion so I welcome anyone else who considers themselves knowledgeable on the subject to chime in, I will personally NOT put up with the mess of Alodine (process) on the outside surfaces because if you are going to do it RIGHT, you ARE going to be taking a chemical bath yourself in the process. It's just plain messy, and review my previous comment about bad stuff getting into hidden places.

I like the 6100 because it's a lot "cleaner" to apply correctly than Alodine, so my intent for the outside finish on my RV is to start with 6100, then go right into a seal coat with DP/LF epoxy primer, then the following day, I'm right into painting.

However, another really good option that would work equally as well for long term durability and protection is, after thoroughly cleaning the bare aluminum with wax and grease solvent, go right into spraying a basecoat of PPG 1791/1792 primer.
That's a very good corrosion resistant primer that, as a primer sprayed on properly cleaned bare aluminum, will offer corrosion protection equal to a metal treatment. Since the 1791/1792 is a true "self etching" primer, it DOES react chemically with the aluminum for the purpose of both corrosion resistance AND adhesion.
As an aside, note that as good as epoxy primers are, they do not "react" chemically with the aluminum. They simply protect, and stick, and promote "sticktion" to what's applied over them, incredibly well because of the physical properties of catalyzed epoxy primers.

Using 1791/1792 means that you don't use any metal conversion pretreatment at all, because it is IMPORTANT to note that when using 1791/1792, the PPG P-sheet for the product says very specifically that "If applying DX1791 to clean, bare metal substrates metal treatments are NOT REQUIRED OR ADVISABLE."
If you're one of those guys who wants to pick up a spray gun and just "get going", this would be a proper way to do it, and the best way to think of using this product is to realize that it simply REPLACES the metal conversion process of Alodine or 6100. After the 1791/1792 is sprayed, you would then spray the DP/LF epoxy primer over it, and then go right into the topcoat paint.

If you think you want to be "safe" by putting 1791/1792 on top of aluminum that you have already treated with ANY kind of metal conditioner like 6100 or Alodine, you'd really be screwing up. Since the 1791/1792 was DESIGNED to be a self-etching primer, it NEEDS bare aluminum to react with, so it would be counter productive to put a barrier between it and the aluminum (i.e., the Alodine or 6100) that would prevent the 1791/1792 from working as it's designed.

One of the reasons why this subject is so never-ending and confusing is because there is no one, exactly correct way to do it. There are several different ways, and they are all good, but once you pick your process, you have to follow it through and stay with all the chemicals and paint that are designed to be compatable with the other parts of the same process.
Changing in the middle, or combining processes (like putting 1791/1792 over aluminum treated previously with a metal conditioner) will cause you lot's of problems.

My personal experiences are mostly with PPG products and I stay with that family of paint products because they make a coating that will paint just about anything.
I have no doubt that Super Koropon is just as good an epoxy based primer as any other high quality brand, but be careful about mixing brands because brand families are designed to be chemically compatable with other products in the same brand. If you use Super Koropon, I'd highly suggest that you stay with the other DeSoto paint products for the rest of the paint process.
DeSoto mentions in their P-sheet (about the Koropon) that it doesn't have to be top coated. However, that's exactly the "feature" I was talking about when I described about how, if the PPG DP/LF epoxy primer is allowed to cure beyond one week, it becomes a "top coat" (for interior use only) by default if not recoated by then.
Speaking of that, note that DeSoto mentions over and over in their Koropon P-sheet that it is an "interior" primer so they are making it clear that the Koropon doesn't have to be topcoated, but ONLY if it's left un-topcoated as an INTERIOR coating which should sound familiar with respect to what I've been saying about the PPG epoxy primer and how it should only be left unpainted if it's used in an interior application.
What all that tells me is that the Korpon and PPG DP/LF are identical products used for the same applications in their respective families of products.

Vern
RV7-A

Pete,

The Sanchem products were developed to promote adhesion for overcoating as well as corrosion resistance, so they should meet your needs well.

The Sanchem 6100 product applies similarly to alumprep/alodine in that the 6100C cleaner is applied with a scotchbrite pad and then rinsed off, followed by the 6100A/B which is applied and rinsed. Like Alumprep, the 6100C is acidic, however it is mild compared to Alumprep and I am told by Sanchem that it should not be a problem on a completed wing. Likewise the 6100A/B. If it seeps into cracks or rivets, and does not get completely rinsed, it should not cause a potential corrosion problem. The Sanchem website shows pictures of the outside of an airliner treated with their product and the painted.

Sanchem seems to recommend that their Seal #2 product be used on top of the 6100 product if you do not plan on overcoating (such as in the interior of wings, etc. This increases the corrosion resistance significantly. If you plan to overcoat with paint, such as the exterior of your plane, then the Seal #2 should not be used so that you get the increased adhesion from the 6100A/B.

When I get to my exterior painting, I plan to follow Vern's advice and use the 6100 immediately prior to priming and then painting within the time period recommeded by whatever paint I decide to use, probably a PPG product as the are fairly readily available.

Anyone want to buy some alodine?

Seal #2

Does the sealer get sprayed or wiped on?

Bob,

I think the Sealer probably works best sprayed. After it is sprayed on you need to heat it briefly with a heat gun to crosslink it. SUpposedly it is quite easy to do. The sealer goes on with a milky color and when it is properly crosslinked it changes to clear so you can tell when it is correctly done.

As soon as I get my order, I test it and see how it works.

Sanchem

Got my chemicals. Hope to test them soon. More after I use them.

Sanchem

I got my Sanchem 6100 as well and will try a test piece this weekend. To reiterate the applicaiotn process:

1. Clean material with 6100C using a scotchbrite pad
2. Rinse 6100C off material
3. Mix 50/50 solution of 6100A and 6100B
4. Apply 50/50 mixture to material using any method you want - brush, sponge, spray, immerse. Material should change color fairly quickly. Allowing 6100 to remain on materail for longer periods does not hurt, but does not help either. Pretty much as soon as the color change occurs, the reaction is complete. Inconsistant color change indicates that material was not cleaned completely- clean again and repeat.
5. Rinse material again
6. Let dry
7. If applying Seal #2 continue with:
8. Apply Seal #2 to dry material. Spraying is propbably best but can be applied with brush or sponge.
9. Let Seal #2 dry on material - should be a milky color
10. Heat material with heat gun - Seal #2 should turn clear

I'll post my results as well.

Post some pictures if you can - I'm interested to see this stuff...

Thomas

Paul,
One little "detail" that could be overlooked is that Sanchem highly recommends using either DI water (deionized) or RO water (reverse osmosis) for rinsing.

I called John Fletcher back after I got my 6100 materials and absolutely no information came with the bottles. I'm a stickler for reading the "P-sheets" of paint and chemical products because that's where you can uncover some less than obvious things that might get you into trouble.

Anyway, so I asked John about the missing P-sheets and he said that the product is so simple to use that you don't need any. However, I kept asking questions and he finally mentioned (almost as an afterthought) that the only guy who had a problem is someone who called him up in a rant and said that the aluminum he was using the 6100 on was looking terrible after he applied it.

It seems that the guy was using hose water from a particularly hard water area and the higher content of minerals in the water was causing the problem. Of course, the guy was "supposed" to know that without being told because, well, the 6100 is so easy to use.
It IS easy to use, but it is just that kind of detail that can bite you in the a** if there isn't a P-sheet to explain it.

I happen to have a RO system in my house so I'm covered. I'll just accumulate a 5-gal bucket of it for rinsing just to be safe.
For the most part, most of us using the 6100 CAN use hose water to rinse with because not all areas have such hard water. Just be aware that if it doesn't go right, you'll have to find some softer (low mineral content) water.

Highflight
RV7-A

Sanchem

Vern,

I too was a bit disappointed that there was no info with the product. You would also think that they would have some sort of printed lables on the bottles rather than just writing the nymbers on with a pen. That makes me a little concerned. I also carefully read all the technical and MSDS and wish they would produce some. Or at least some printed usage instructions. I called John Flitcher yesterday as well to review the procedures prior to posting them and he made no mention of DI or RO water. I don't have either available, but I don't think the water here is very hard so we'll see. This could be a drawback to the product. I'll try a small test piece tonight and see what happens.

I do not trust them?

I called them as well and I spoke to the guy. I wanted to get safety sheets and application instructions for the conversion product and the sealer. He said he would send it with the product once I order. I wanted him to fax it or e-mail it before I buy it. Every time I got to that topic he would change the subject. So, as a result I do not trust them now, especially that now I see they have never sent the instruction or safety sheets to people who ordered their products. Good luck experimenting?.

Andrzej

Vern,

WOW! Thanks a lot for the dissertation. That was most enlightening.

I'm gonna paint my pieces as they are completed so I will follow the guidlines for sure. My understanding of these processes has certainly been enhanced.

Cheers, Pete

Follow-up on Sanchem 6100?

Does anyone have anything to report on the Sanchem system? How did the tests go?

Tom Maxwell said:

Does anyone have anything to report on the Sanchem system? How did the tests go?

Click to expand...

Not yet... Due to personal issues involving storage considerations and available space to build, I am only now about to start work on the empennage for my QB kit. I won't be actually pounding rivets for about another month or so, and then it's pedal to the metal.

I'll have some comments in a couple of months.

Something else to consider

My 1975 Cessna 150-M is not primed internally and has no corrosion as attested to by the guy who stripped and painted it in 2001. Every few years my A&P sprays an oil fog inside the tail cone, wings, empennage, etc. DON'T DO THIS BEFORE YOU PAINT. I use a similar technology to keep my car rust free in the Detroit (salt capital) area. I do the car annually. It drips forever, but it works and in the aircraft, probably handles scratches and metal-to-metal joins better and lighter than painting. That said, I primed wherever my internal parts make contact with each other, but not on the inside skin surfaces. My QB came with primer just about everywhere.

Just FYI.

FWIW, I prepared all of my parts (so far). Alumiprep -> Alodine -> primer on all of the internal parts (ribs, etc.). For the skins, I primed both sides prior to riveting.

Why? Well, once you hook up the paint gun, and mix a little primer, it's just not that much more work to prime the skins both sides. It does use up primer, but for the rudder and VS on the -10 I only used about a 1/2 cup of mixed primer for the skins - pretty cheap if you ask me.

Does it really matter? I honestly don't know. However, I have two aluminum screen doors on my house in FL that are 20 years old. Both were pretty high quality doors, and both are falling apart from corrosion and will have to be replaced soon. Priming will certainly make me feel better

As for the fog spray into the Cessna, I'd love to hear more about that!

Ken
RV-10 40439
HS almost done.

I didn't prime the skins on the emp (I did use the Alodine pen in some cases). but I got to thinking while building the "new" rudder the other day....man, this is easy. Why should I prime these parts and add this weight. It takes about 16 hours (or less) to build the rudder. If the thing should corrode, I'll just build a new one.

Got2Fly said:

As for the fog spray into the Cessna, I'd love to hear more about that!

Click to expand...

I own a very clean though unprimed 1966 C-150F that was beginning to show the first signs of corrosion discovered at annual in 2002. The shop urged and I had that corrosion treatment spray applied as well.
It cost about $200 bucks. That stuff really penetrates into all the nooks and crannys and continued to ooze from most of the skin seams for over 2 years.

Rick Galati RV-6A "Darla"
C-150 N3107X "2"SMOH

Acf-50

The "fog" is usually ACF-50 a penitrating corrosion inhibitor thats is sprayed into airframes. Another brand is Boeshield that was developed by Boeing. Either product is very penetrating. Oh and I almost forgot about corrsion X.

I also own a 1976 Cessna 150/150 and I live in FL where it is very humid. I usullly apply Boeshield at least every other annual. After application the stuff litteraly oozes from everywhere for at least a year or more. It's amazing how well it works itself into all of the "nooks and crannys"

Due to my location I'm priming EVERYTHING. Even so I may still apply the Boeshield after I'm flying..

Where can I buy Sanchem 6100?? I checked AS and vans.

Thanks
-Ron

After priming all my skins for the empennage and wings and every other part that goes into the airplane thus far I have changed my mind about priming. My old nearly 50 year old Cessna 172 was in very good shape with almost no corrosion after all those years. I read where Van's used Sherwin Williams P 60 wash primer on all their quick build kits so I figured that was good enough for me. After I did all that cleaning and painting I read that Sherwin Williams offers little corrosion protection if not top coated. I'm sure it will do some good. For the fuselage I will prime anything that is not alclad with some form of epoxy primer and forget the rest. After the plane is built and painted I will treat the interior of everything with corrosion-X or other similar product. In 50 years or so we'll see how it works. I might live a little longer not being exposed to those paint products too. Anyway, that's my story and I'm sticking to it.

Jim Wright 90919 RV-9A Wings Arkansas

More about fog spray

Got2Fly said:

As for the fog spray into the Cessna, I'd love to hear more about that!

Click to expand...

My A&P/AI says:
"The CRC product meets the same Mil spec, but now I believe it is not as good as Corrosion X or ACF 50.

It is best if fogged in for full coverage. A high pressure pump through a small hole at the end of a wand (about 6 feet long) does it."


h