What to use to treat minor corrosion on Spar

[southwind32]

Found a critters nest in the wing. Cleaned it out and found some very minor surface corrosion. Cleaned it up with MEK and a scotch brite pad. I'm looking for suggestions for what to use to treat and protect the metal. I don't want to paint it.
Thanks
Brian

[Esser]

I used epoxy primer on mine

[HighWing]

When I was first building in the late 90s there were products that were used to coat aluminum to prevent corrosion. Checking in Aircraft Spruce, the original brands are not there, but the current materials are BONDERITE C-IC 33 AERO and BONDERITE M-CR 1201 AERO. The first is a prep compound that will remove all corrosion and the second is a conversion coating that will create a chemical surface that is resistant to corrosion. It is frequently used to prevent corrosion in the wings of certified aircraft. Instructions are in the listing at ACS. I used it frequently in the old days as I was always adding things to the airplane and didn't want to paint.

[N213RV]

When I was first building in the late 90s there were products that were used to coat aluminum to prevent corrosion. Checking in Aircraft Spruce, the original brands are not there, but the current materials are BONDERITE C-IC 33 AERO and BONDERITE M-CR 1201 AERO. The first is a prep compound that will remove all corrosion and the second is a conversion coating that will create a chemical surface that is resistant to corrosion. It is frequently used to prevent corrosion in the wings of certified aircraft. Instructions are in the listing at ACS. I used it frequently in the old days as I was always adding things to the airplane and didn't want to paint.

If you don't want to paint it, then acid etch and alodine might be a good approach.

[jiott]

I also used epoxy primer on my aluminum spars, inside and out. Figured someday I may want to put floats on, or operate near salt water.

[southwind32]

I also used epoxy primer on my aluminum spars, inside and out. Figured someday I may want to put floats on, or operate near salt water.

Jim, I'[m curious, how did you paint the inside of the spar?
Also, when you sprayed the outside, did you paint the wood ribs too, or did you cover the wood or ??

Thanks
Brian

[ken nougaret]

Jim, I'[m curious, how did you paint the inside of the spar?
Also, when you sprayed the outside, did you paint the wood ribs too, or did you cover the wood or ??

Thanks
Brian

I used an airbrush on a long piece of pvc with epoxy primer to coat the inside of my spars. Ken

[jiott]

I painted the inside by putting a tennis ball in one end and pouring some primer in, then jam another tennis ball in that end and tip and slosh the primer all around, then pour out the excess.

The outside was painted by brush after the ribs were all glued in and varnished. I did not paint over the varnished ribs.

[Northof49]

Alodine is for aluminum ,just be sure to remove all the black pitted in the corrosion.

[jmodguy]

What color Scotch brite pad did you use?

[DesertFox4]

What color Scotch brite pad did you use? Jeff, I was wondering the same thing.

[dholly]

What color Scotch brite pad did you use?
Use the maroon color pads (item #7447) only, they are manufactured with a very fine grade aluminum oxide grit abrasive. Do NOT use the gray pads (item #7448), as they contain silicone carbide grit abrasive. The silicone carbide could break down and stick in the aluminum causing corrosive stress points, very much like marking aluminum spars with a pencil is a no-no (use ball-point or felt tip pens when marking on bare aluminum!).

[southwind32]

What color Scotch brite pad did you use?

The maroon colored

[dholly]

@Brian-

This was a topic recently on the AvidFoxForums. Forgive the lengthy and partially duplicative reply, but it is easier to simply copy n paste. All you ever wanted to know about mouse urine:


What I've read suggests that simply attempting to neutralize the alkaline salts with an acid is not enough to prevent corrosion. Here's what I found:

When urine is deposited it has a pH between 5 and 6 (slightly acidic due to Uric Acid). As it dries, the urea is broken down by the bacteria (that decomposition is what makes it smell like ammonia) and it turns into an alkaline salt with a pH between 10 and 12 (strong alkaline). Urine is the only product in nature that changes from an acid state to an alkaline state. Who knew?

Urine is composed of things that REQUIRE enzymes to break down the chemical bonds. Soap, vinegar, baking soda, ammonia, chlorine, and hydrogen peroxide are not chemically capable of breaking down the uric acid. Home-made mixtures or typical household cleaners made from these simply do not contain the required ingredients to remove all the components of urine. Urine is composed of:

• Urea
• Urobilin/Urobilinogin
• Uric Acid
• Sodium
• Other electrolytes
• Creatinine
• Pheromones
• Bacteria – typically 5 different strains.

The urea and urobilin/urobilinogin are not hard to clean. Urea, urobilin/urobilinogin, creatinine and the pheromones are water soluble (urobilin is the pigment that causes the color). Traditional household or carpet cleaners will deal with these and this is why some appear (initially) to be effective at eliminating the problem. But the problem has not been solved! Uric acid and its salts have been left behind. Uric acid is not water soluble and bonds tightly to whatever surface it touches.

The only thing that will break down the uric acid to permanently remove the smell and stop corrosion is an enzyme cleaner. The enzymes penetrate, consume and break down uric acid molecules into carbon dioxide and ammonia, both gasses that then easily evaporate. This is why it is also essential to allow the enzyme cleaner to air dry. It needs the “natural” drying time to break down the uric acid salts, allowing the resulting gases to evaporate. Protease is the enzyme that breaks down protein stains like urine best, although amylase, which breaks down starch, may also help.

I was thinking about the mouse pee issue again, you absolutely need to stop the caustic corrosion as washing and rinsing just doesn't do it. The only way to guaranty permanent elimination is with a enzymatic cleaner that pulls the pee out and eats it up. Yum.

So anyhoo, my mind turned to the 'Nature's Miracle Super-Oxygenated Stain & Odor Remover' product we used to clean up after one of our Black Labs suffered from canine epilepsy. It is an oxygen-infused, bio-enzymatic formula designed to react to organic stain and odor matter and works to eliminate any traces of urine, feces, drool, vomit and other pet messes, strong pet urine odors, yellow stains and the sticky residue left behind after pet urine is efficiently removed. Great stuff, we bought it by the gallon and couldn't live without that and the carpet steamer. (R.I.P. Sophie Girl ^-^).

Thinking it might be worth following up on, I posted the question to the manufacturer's online "Ask The Expert" FAQ forum and got an answer:

Q.) Hi, I have found mouse nests, droppings and urine in my stockpile of 2.5" dia. x .065" wall 6061 T6 aluminum tubing. Which product(s) would be best for cleanup and effectively neutralizing the long term corrosive effects of mouse urine? Thank you.

A.) Thanks for asking! The best product to tackle the mouse mess is our Advanced Stain & Odor Remover. As long as it remains wet it will continue to 'eat' the urine until it is completely eliminated. You may want to use a garden sprayer, or purchase one of our battery powered units, to make sure the spray reaches the inside of the tubing.

Wife says it cost about $20-25/gal. at WallyWorld, PetSmart etc. Don't buy the Advanced Formula, it just adds some fragrance which we found both redundant and unnecessary as you are eliminating all odor anyways (kudos to the marketing team I guess). So there you have one good, cheap (at least, relatively to the AlumiPrep/Alodine treatment) mouse pee neutralizing option that should work and provide peace of mind. You sure don't want to fly or pass along a plane knowing it has a spar corrosion issue when it can be resolved so easily, IMHO. According to the Directions you must saturate the areas, maybe more than once, and let dry naturally. Best to treat your wings ASAP so the ribs will be completely dry by recovering time.

Directions:

(Stain Removal) Wipe away any excess stain-causing material, and then soak the surface thoroughly with Nature’s Miracle Stain and Odor Remover. Wait 5 minutes, and then wipe away stain with a cloth. For tough stains, use a stiff, bristle brush. If the stain is not completely removed, re-soak area and allow Nature’s Miracle Stain and Odor Remover to work for 1 hour before wiping with a cloth.

(Odor Elimination) Thoroughly soak the entire area with Nature’s Miracle Stain and Odor Remover. For carpets, apply enough to reach the urine penetration in the pad and floor. This may mean lifting the carpet and applying directly to the pad and floor. Allow the product to air dry. Depending on air circulation, carpets and upholstery may take up to 2 weeks to dry completely. If after 2 weeks there is still an odor, Nature’s Miracle Stain and Odor Remover has not reached ALL of the odor-causing material. Pinpoint odor source and repeat cleaning process. Keep the product away from children and pets and do not allow pets onto the treated area until it is completely dried.

Tips:

Always test surfaces to be treated for color fastness by applying to a hidden area and wiping with a cloth. If color is removed from the test area, do not use Stain and Odor Remover on this surface. Always use Stain and Odor Remover at full strength for best results. Use Nature’s Miracle Stain and Odor Remover before any other product as cleansers and detergents may chemically “set” the stain.
Stain and Odor Remover is not recommended for use on silks, leather, or suede.

[jmodguy]

Maroon colored scothbrite is the proper use for aluminum!
If you really want to know how to treat this, or any other corrosion, see if you can dig up the latest (or recent) copy of NA 01-1A-509.
This is the US Navys corrosion control Bible. I still refer to it for corrosion control issues.