Paint stains

[Nukemzzz]

We are coming out of winter and I found a good social distancing activity is washing the airplane because nobody wants to help. While getting up and personal I noticed lots of circular dark spots in the paint that have an organic appearance. My best guess is this plane spent part of its life under a hanger that had birds roaming around. Actually, the logbook shows this plane spent about a decade once waiting for a new engine after a prop strike and this probably happened in storage. Any advice on how to remove these?  I’ve tried 3M adhesive remover, WD-40, simple green, and of course soap.  I’m afraid to try diluted bleach. 
 

 

[MikeOH]

Have you tried 100LL?  I know those aren't fuel stains, but it might be worth a try.

[carusoam]

Look real close...

Bird droppings tend to leave an etch mark where the paint gets removed by the acidic droppings...

There are a few posts in a thread around here Called paint corrections... that may be helpful...

If the paint is in good condition... a cleaner / wax can be helpful... keep in mind it removes a fine layer of paint is why it works...

PP thoughts only, not a paint technician..

Best regards,

-a-

[tmo]

You could also try to become friends with @Denver98...

[Denver98]

5 hours ago, tmo said:

You could also try to become friends with @Denver98...

One Mooney polish is enough!  

The best ways to attempt to remove those stains, start with a clay bar, that should remove most of the surface staining.  To get the deeper staining, use a good step 1 compound with an aggressive pad on a random orbit polisher.  Once you’ve chased that rabbit down the rabbit hole, in only 60 more hours your airplane’s paint will look GREAT!  

I recommend Adam’s polishes waterless wash, medium clay bar,  and compound with Adam’s one step pad.  If you want to go all the way, use their polish and ceramic coating.  Their Micofiber detailing and polishing towels are the best I’ve ever used.   They run specials and discounts from time to time.  If you call them they should give you a good discount.  I’ve yet to pay full price for a product, but I have spent a LOT on their products.

If you need more help, I recommend calling their Thornton, Colorado store and ask for Charlie.  He’s helped me for the last couple of months.  Pretty sure I’m know as the “guy polishing an airplane”.  Wouldn’t be surprised if they use the word crazy in there as well.  

Best of luck. 

[Frank B.]

So, .... here I go giving away one of my best kept secrets. 
 

https://www.ebay.com/p/21016380059?iid=161864101210&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=161864101210&targetid=886274372555&device=c&mktype=pla&googleloc=9011523&poi=&campaignid=9418895003&mkgroupid=92907999782&rlsatarget=pla-886274372555&abcId=1141016&merchantid=6349974&gclid=CjwKCAjwg6b0BRBMEiwANd1_SKFrILf3-H-IeYoI0KU9y6w9y12S0Y3sRrombgTwGt-8ot8dX8JychoCYhgQAvD_BwE

We use this product in our business and I always keep a case at my hangar. 

[N201MKTurbo]

56 minutes ago, Frank B. said:

So, .... here I go giving away one of my best kept secrets. 
 

https://www.ebay.com/p/21016380059?iid=161864101210&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=161864101210&targetid=886274372555&device=c&mktype=pla&googleloc=9011523&poi=&campaignid=9418895003&mkgroupid=92907999782&rlsatarget=pla-886274372555&abcId=1141016&merchantid=6349974&gclid=CjwKCAjwg6b0BRBMEiwANd1_SKFrILf3-H-IeYoI0KU9y6w9y12S0Y3sRrombgTwGt-8ot8dX8JychoCYhgQAvD_BwE

We use this product in our business and I always keep a case at my hangar. 

It is not advised to use alkaline cleaners on aircraft. Products like Formula 409  and such work great, but can cause your aluminum to corrode. People freak out about Simple Green which is very mild and you step up with the big guns!

[carusoam]

visiting the eBay site, I quickly found that the cleaner was an alkaline cleaner...

So I asked Siri...  alkaline and aluminum.

She gave me this... (pretty much what Rich said above, with more words)

-a-

 

Q. We use an aqueous alkaline cleaner to process parts with ultrasonics and filtered circulation. The process does well on stainless steel parts, but I have an issue with aluminum parts, using the same parameters, minus the ultrasonics. The aluminum parts come out of the bath with dark, black streaks and spots. Should I not use the same bath to process aluminum and stainless steel? Can aqueous alkaline cleaner be used on aluminum? 

A. Probably not. Cleaners that are formulated to clean metal like stainless steel usually cannot be used for aluminum. Since industrial processing of stainless steel (forming, bending, cutting, etc.) is typically more demanding than a similar operation for aluminum, the lubricants used can be difficult to remove. Therefore, most aqueous alkaline cleaners formulated for use on stainless steel have a high pH and will contain quite a bit of free caustic in the form of sodium or potassium hydroxide (in addition to ingredients like surfactants and buffers).

 

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If a cleaner like this is used on aluminum, it tends to etch the surface. This condition will be made worse with elevated temperature and longer periods of time. Additionally, the higher the concentration of the cleaner, the worse the etching and discoloration.

Free caustic will quickly reduce the naturally-occurring oxide on aluminum and immediately start to etch and dissolve it. Most industrial aluminum is alloyed to attain specific properties (typically with copper, manganese, silicon, magnesium and zinc). The discoloration of the aluminum is the presence of the undissolved alloying elements and the secondary phases that they form that are not attacked in the high pH bath. They wipe off fairly easily, although chemical removal is generally only attained by use of an acid (like nitric) to dissolve these alloying elements. 

[tmo]

My initial reaction was similar (this post came in as I was searching around for "household cleaners safe to use on airplanes"), but the Safety Data Sheet for the cleaner claims: Not corrosive to SAE 1020 Steel or non-clad Aluminum based on test data (UN Manual of Tests and Criteria, Part III, Section 37.1 -Corrosion to metals).

Edited April 5, 2020 by tmo

[Danb]

On 4/4/2020 at 2:32 PM, Nukemzzz said:

We are coming out of winter and I found a good social distancing activity is washing the airplane because nobody wants to help. While getting up and personal I noticed lots of circular dark spots in the paint that have an organic appearance. My best guess is this plane spent part of its life under a hanger that had birds roaming around. Actually, the logbook shows this plane spent about a decade once waiting for a new engine after a prop strike and this probably happened in storage. Any advice on how to remove these?  I’ve tried 3M adhesive remover, WD-40, simple green, and of course soap.  I’m afraid to try diluted bleach. 
 

 

Get the proper tools, I like Meguiers and Griots polishing compound, good wax and sealants should work. I do mine every six months. During our pandemic you should have time that bird can look great with a little work

[PT20J]

5 hours ago, tmo said:

My initial reaction was similar (this post came in as I was searching around for "household cleaners safe to use on airplanes"), but the Safety Data Sheet for the cleaner claims: Not corrosive to SAE 1020 Steel or non-clad Aluminum based on test data (UN Manual of Tests and Criteria, Part III, Section 37.1 -Corrosion to metals).

Not sure what they mean by non-clad aluminum. Pure aluminum is very corrosion resistant, but not very strong. Alloyed aluminum is stronger, but not as corrosion resistant. Cladding is a coating of pure aluminum over an aluminum alloy to improve corrosion resistance. Skins are 2024-T3 Alclad aluminum. 

Any metallurgists onboard? 

Skip
 

[Nukemzzz]

Wow...thanks for the responses. I’m going to try 100LL first since the paint is clearly designed to resist it and it’s highly solvent for many things.