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Zinc Chromate Okay?

D

donoltman

Active Member
After flying a Comanche 250 around for 6 years it has been sold and there is a RV-10 tail kit on my hangar floor. Work tables built and inventory done. It never ceased to amaze me at annual to look down the tail of a 50 year old airplane and see yellow Zinc Chromate on skins that looked like they just rolled off the floor. Considering it works so well, what could possibly be the drawback to just doing the same thing on my 10? It seems like there a ton of threads on about every kind of primer in the world but doesn't the yellow work just as well? What am I missing? Not priming is out of the question. No corrosion in 50 years has made a believer out of me.

Don Oltman
 
Zinc chromate is fine and has worked for years.
It was developed many years ago. It is fairly heavy and easily scratched. There are much better primers available today.
 
What Mel said.

Also, zinc chromate is known to be carcinogenic. So if you do use it, be sure to take precautions to avoid inhalation and skin contact. Having said that, taking those precautions would still be a good idea even with more benign primers.
 
Mel said:
There are much better primers available today.
Click to expand...

OK Mel - which in order of your preference are the better primers?
I am aware I risk all the comments about igniting primer wars, but I would value Mels opinion on this and hope he will give said opinion.
I have been wondering about weight of primer and plan to prime mating surfaces.
John
 
rjtjrt said:
OK Mel - which in order of your preference are the better primers?...
Click to expand...

Whew, what I have been waiting for all these many years. Finally I will get the definitive answer on primer. You're up Mel.
 
WELL...........

One of the reasons I avoid the "primer wars" is that this is one of the places that I don't "go with the flow".
I'll let you other guys put up all your opinions and disagreements.

I've been using Sherwin Williams vinyl wash primer on airplanes and cars since the early 1980s. I've had discussions directly with Sherwin Williams engineers and they have told me nothing to make me change my mind.

It's expensive and it can be "nasty" to your lungs, but used properly it's light weight, takes very little material, and is almost impossible to scratch.

It has incredible adhesion properties, especially with aluminum, steel and magnesium.

I will not enter a debate. This is what I use and I like it.
You use what works for you.

And while I'm on the "box" I'll stir one more pot and say, I NEVER use rattle can primers. No one has ever convinced me that they are truly "self-etching".

There's something to be said about using nothing. It's cheaper, lighter, much less work. Most aluminum in RV kits is alclad 2024 and the rest is 6061 which is very corrosion resistant already.
 
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Zinc Chromate

Mel;
I don't want to get anybody upset, I am just trying to make a primer decision and stick with it until the end. Unfortunately, the only experience I have is a good one with the yellow. Assuming that I would use a couple of gallons of primer, what do you think the difference in weight would be between the yellow and the Sherman Williams product? Thanks
Don
 
That's almost impossible to determine. It's very easy to use 3 to 5 times the amount necessary.
With the wash primer, you need only a very light film. Most people use at least twice the needed amount. The way I judge is hold a piece of bare aluminum up next to the primed piece. If you can see a difference, you have enough.

If you are comfortable with zinc chromate, then go with it. It certainly works.
 
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Zinc Chromate

The same formulation used in WWII and that we older troops used is now hard to find. There are other formulations now that have zinc oxide, or XXX in the title. This was done in an effort to make a safer product, especially rattle can types.

You can make yourself very ill with this. I got a case of tolulene poisoning years ago while priming a plane. I was out of action for several days.

'No primer ' works pretty good. I had an unprimed 1939 Luscombe that was as clean as a new RV part. I also explored a C-47 wreck in the Rockies that had crashed in WWII. It had been fully exposed to the elements and was also very clean after >50 years exposure.
 
Oh wow - I hope this gets moved to the never ending debate section.

I'm getting the popcorn off the shelf. It's sitting on the same shelf and just to the right of my chromate version of Variprime.
 
Count me in

As another beginner. Mel, I just googled Sherman Williams Vinyl Wash Primer and there are quite a few of them for sale. Please guide me to the 'right one' - please list the SW product by catalog number. Your recommendation will end my primer search. Thanks very much.
 
I'll have to go to the shop in the morning and check the numbers.

We recently have a skunk residing close by. He's on our back porch every night. I won't venture out there in the darkness until I know he's not around. I have set out poison. We'll see!

Found the numbers in my file. Wash Primer E2 G 973. Reducer R7 K 242.
It's been a number of years since I bought. Numbers may have changed.
 
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Primer

Phil said:
Oh wow - I hope this gets moved to the never ending debate section.

I'm getting the popcorn off the shelf. It's sitting on the same shelf and just to the right of my chromate version of Variprime.
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I like my popcorn white and my primer green. My popcorn sits right next the Nason self etching primer. It is a Dupont product and some people like it because it is very close in color to green zinc chromate. I will admit that it is hard to beat Variprime. If I was using Variprime I would see if the paint store could tint it green.
 
E. D. Eliot said:
As another beginner. Mel, I just googled Sherman Williams Vinyl Wash Primer and there are quite a few of them for sale. Please guide me to the 'right one' - please list the SW product by catalog number. Your recommendation will end my primer search. Thanks very much.
Click to expand...

Don't know which is Mel's "right one", but the Sherwin Williams vinyl wash primer that Van's uses on the quickbuilds is part number P60G2.

Now if you really want the "right one", consider using a 2-part epoxy primer. :cool:

Uh oh, primer war threat level going to orange! :eek: :p
 
It's called Sherwin Williams Corrosion Shield E2G973.
Reduce with R7K242, 1.5:1 (Reducer includes catalyst)

Not sure about P60G2, but I suspect it's close if not the same.
 
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Thanks Mel

Appreciate the great and amazingly quick answer! I'll look it up at our local SW distributor tomorrow. Thanks again, Ed
 
Primers

Sherwin Williams does make a zinc chromate primer CM0723404. However, as Mel says there are lots of better products. Read the product data sheets carefully. The zinc chromate primer says excellent for water and corrosion resistance. The epoxy primers say excellent corrosion and chemical resistance. If you ever spill anything such as fuel, oil or hydraulic fluid inside your plane, I think the epoxy primers offer the best protection as well as against water and corrosion.
 
primer

I had no idea that there were so many variations being sprayed. It makes sense that the zinc chrromate has been dumbed down from the original. Since I really don't want to get sick, I'll slide into Shermin Williams also. Thanks for all the help.
Don
 
Be sure to use a good carbon respirator.

donoltman said:
I had no idea that there were so many variations being sprayed. It makes sense that the zinc chrromate has been dumbed down from the original. Since I really don't want to get sick, I'll slide into Shermin Williams also. Thanks for all the help.
Don
Click to expand...

All these primers can be hazardous to your health!
 
My 2 cents.

johngoodman said:
Leave the Alclad on, and use CorrosionX a few years down the road after it's flying.
http://www.corrosionx.com/corrosionx-aviation.html

John
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Not to drive the thread into the realm of primer wars, but I agree with John. I have done tons of research and cannot find a good reason to use SE primers unless you intend to topcoat them with a paint. They eat into the Alclad (which IS a corrosion barrier) and don't prevent water intrusion without a topcoat. Therefore (IMHO) they simply hide the corrosion instead of preventing it. That said, zinc chromates seem like a good option, but given the extra money, time and health concerns (most people build at home), I think the costs outweigh the benefits. My vote is to use Van's recommendations, which in most cases means nothing but Alclad. It's lighter, cheaper, healthier and faster to build. My $0.02.
 
DaAV8R said:
I like my popcorn white and my primer green. My popcorn sits right next the Nason self etching primer. It is a Dupont product and some people like it because it is very close in color to green zinc chromate. I will admit that it is hard to beat Variprime. If I was using Variprime I would see if the paint store could tint it green.
Click to expand...

My variprime IS green:
29smso.jpg
 
I use Zinc Chromate rattle cans. I started off with the yellow and switched to the green. It does scratch off fairly easy, but the advantage is ease of use and almost no cleanup. For me, I know it was the right choice.
 
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