[Space Cadet]

Hey all,

Have just about finished prepping the entire emp for batch job priming, and even run one batch through the entire process for learning. Everything was going mostly smooth, but the last thing to be cleaned, the skin interiors, just will not come clean (with MEK). Used the same process for all the parts- wash with Dawn and rinse, dry, then wipe with MEK. Getting a dark residue no matter how many times I wipe them down, have tried more MEK, letting it soak a bit, and I am using clean rags regularly. It's not primer residue from the first batch, as it is not green and a little of that already came off easily. No difference from all the other parts that I can tell...

Any ideas?

Thanks!
Dwight

 

[TSwezey]

Try acetone.

 

[L.Adamson]

Try some "gray" scotchbrite pads. Every surface that I primed or painted, ended up with scotchbrite somewhere along the line.

Paint stores have large pads, and Home Depot has smaller ones.

L.Adamson -- RV6A

 

[Space Cadet]

"Try some "gray" scotchbrite pads. Every surface that I primed or painted, ended up with scotchbrite somewhere along the line."

You mean beyond the regular (purple) scothbrite work already done to scuff everything?

 

[Sam Buchanan]

Hey all,

Have just about finished prepping the entire emp for batch job priming, and even run one batch through the entire process for learning. Everything was going mostly smooth, but the last thing to be cleaned, the skin interiors, just will not come clean (with MEK). Used the same process for all the parts- wash with Dawn and rinse, dry, then wipe with MEK. Getting a dark residue no matter how many times I wipe them down, have tried more MEK, letting it soak a bit, and I am using clean rags regularly. It's not primer residue from the first batch, as it is not green and a little of that already came off easily. No difference from all the other parts that I can tell...

Any ideas?

Thanks!
Dwight

Coleman Lantern Fuel is great for cleaning skins since it leaves no residue once all the dirt is removed from the skins. Careful, obviously it is quite flammable.

 

[Mel]

Clean first:

Clean the surfaces before scotchbrite. If you don't, the scotchbrite will grind the oils into the aluminum.

 

[L.Adamson]

"Try some "gray" scotchbrite pads. Every surface that I primed or painted, ended up with scotchbrite somewhere along the line."

You mean beyond the regular (purple) scothbrite work already done to scuff everything?

No, I just always prefered the gray over purple to start with. Gray is a bit finer...........I think

 

[Space Cadet]

Mel-

That is probably it. Was doing it in the wrong order, too late now (all done scuffing). Any good fixes, or just keep scrubbing?

D

 

[L.Adamson]

Mel-

That is probably it. Was doing it in the wrong order, too late now (all done scuffing). Any good fixes, or just keep scrubbing?

D

Just re-reading your post. Is the dark residue just on the cleaning rags, as they wipe across the aluminum surface? If so, it's normal.

As to cleaning for oil; yes I would clean the parts first, before scotchbrite. However, all parts won't be necessarily be contaminated by oils to begin with. Unless of course, oily fingers, oily tools, or oily machines that process parts.

L.Adamson

 

[az_gila]

Acid etch

Try wetting your Scotchbrite pads with acid etch as you scuff... ....then rinse well.

Buy at your local auto paint store... gil A

 

[Space Cadet]

Just re-reading your post. Is the dark residue just on the cleaning rags, as they wipe across the aluminum surface? If so, it's normal.

As to cleaning for oil; yes I would clean the parts first, before scotchbrite. However, all parts won't be necessarily be contaminated by oils to begin with. Unless of course, oily fingers, oily tools, or oily machines that process parts.

L.Adamson

Try wetting your Scotchbrite pads with acid etch as you scuff... ....then rinse well.

Buy at your local auto paint store... gil A

L. - Yes, it is, but I'm thinking it's not normal- the surface needs to be clean, no? All my other (non-skin) parts came clean (on rags) with minimal work. The skins just keep showing the residue on the rags.

Gil- Sounds like that might work. Also considering stronger bath with the soap (maybe soaking a bit), and wondering whether alodining over it might take care of the issue altogether?

Dwight

 

[L.Adamson]

L. - Yes, it is, but I'm thinking it's not normal- the surface needs to be clean, no? All my other (non-skin) parts came clean (on rags) with minimal work. The skins just keep showing the residue on the rags.

And they probably always will show a residue until coated with something.

I just went out to the garage and pulled out an old wing skin, that I replaced. I scrubed it with soap & rags. Got residue.

Then I scrubbed it with Coleman lantern fluid, and got residue.

Next came the scotchbrite pad in soap and water, and got more residue. Followed by more Coleman fluid, and still more residue.

Now to the laquer thinner & acetone. Still more residue....

I figure that I can scrub until no aluminum is left, before all signs of "dark gray" residue are gone!

The other side of this skin was coated with a two part epoxy primer, about 10 years ago. It looks just fine.

L.Adamson -- RV6A

 

[az_gila]

Acid etch

.....
Gil- Sounds like that might work. Also considering stronger bath with the soap (maybe soaking a bit), and wondering whether alodining over it might take care of the issue altogether?

Dwight

Alodine won't properly work unless the surface is really clean... hence the recommendation for acid etch before alodine.

I just acid etched old parts for one of my tanks before proseal assembly - it really cleaned up the old skins and ribs. If you create any residue during etching, it's washed off in the rinse process, since you shouldn't let the acid etch dry on the surface...

gil A

 

[dougweil]

Cleaning

For priming I have used this process and never had an issue:

1. Clean with PPG Wax and Grease remover or Dupont 3812S reducer.

2. ScotchBright purple pads

3. Clean again with PPG or 3812S

4. Prime (I use NAPA 7220 self etching primer)

You are done.

 

[Space Cadet]

Thanks to all!

And they probably always will show a residue until coated with something.

I just went out to the garage and pulled out an old wing skin, that I replaced. I scrubed it with soap & rags. Got residue.

Then I scrubbed it with Coleman lantern fluid, and got residue.

Next came the scotchbrite pad in soap and water, and got more residue. Followed by more Coleman fluid, and still more residue.

Now to the laquer thinner & acetone. Still more residue....

I figure that I can scrub until no aluminum is left, before all signs of "dark gray" residue are gone!

The other side of this skin was coated with a two part epoxy primer, about 10 years ago. It looks just fine.

L.Adamson -- RV6A

Alodine won't properly work unless the surface is really clean... hence the recommendation for acid etch before alodine.

I just acid etched old parts for one of my tanks before proseal assembly - it really cleaned up the old skins and ribs. If you create any residue during etching, it's washed off in the rinse process, since you shouldn't let the acid etch dry on the surface...

gil A

Good input from everyone. I'll take the safe (and not too tough) route of using the acid etch to clean it up prior to final priming. Really appreciate the help. Whew, stress levels reducing...

Dwight