Removing Paint From Aluminum - My thoughts

[labattomy]

I see some people mentioning using a wire wheel to clean paint off the aluminum boat and I just want to caution you that if you use a ferrous wire wheel brush, minute particles of the steel in the brush comes off in the aluminum and then interstitial corrosion begins.
This is a serious problem and at this point the boat is almost ruined.

I say almost because I have heard of some type of solution you can put n the aluminum to stop the corrosion, but eventually the skin will corrode and weaken.

I know this because I have experience with aircraft stressed aluminum skin - and when you use the wrong wire wheel on the aluminum, the plane is basically considered not airworthy.

If you must wire wheel, make sure you get a stainless steel wheel (not a cheap harbor freight stainless, get a good one (it will cost you)
Sandblasting is too aggressive, Bead blasting and walnut shell blasting might be OK, but I am not a fan of the damage these types of abrasives do the aluminum.

or better yet, use the aircraft stripper to remove the paint and save the skin underneath.
That is what the aircraft mechanics do for refinishing planes...

Any other thoughts are welcome and I am sure there are tons of posts about this very topic all over iBoats by people much more knowledgeable than I,

Dan

 

[JoeMan]

Re: Removing Paint From Aluminum - My thoughts

Completely agree. The 10 dollar cans of aircraft stripper are far more than worth it, and I've found no better product to get paint off of aluminum.

My brother and I have also used another process, and very successfully. They make a spray fixture for compressors which is used primarily to strip paint and other material from concrete/bricks. Using the garden hose hooked to the house spicket and a bucket of sand, it blasts the paint from the aluminum leaving it paint free and very clean without warping the aluminum, due to the cooling effect of the water. I did this on my Duratech hull with very good results...my brother has been restoring aluminum boats for nearly 20 years and has done this many times without regret or issue. Some sand media is too rough for the job and chips up the aluminum which you do not want, other is too wimpy and takes forever...you need a medium coarse grade sand. This process left my hull nice and velvety, ready for primer.

 

[hlolver]

Re: Removing Paint From Aluminum - My thoughts

I am not experinced with any of this stuff, could you explain again the "sand blasting" technique mentioned above?

 

[JoeMan]

Re: Removing Paint From Aluminum - My thoughts

Yep. The main tools here are a 2000 psi (or higher) compressor/pressure washer, water source (your garden hose hooked to the house), and the masonry tool mentioned above in this thread. You may be able to rent the masonry tool, call around to see if some rental place offers one along in addition to the pressure washer. If they're not sure what you're referring to, tell them that the masonry blasting tip replaces the pressure washer gun, and that it comes with it's own hose (dry) which draws in sand from a bucket. The pressure of the water blasting through the masonry tip is also serving to cause a suction force (I refer to this as the venturi effect) which draws up the sand from the bucket, then the masonry tool is blasting a high pressure mixture of the sand and water together out of the tip. Make sense? I'm glad to talk to you via phone if it helps - IM me and I'll provide my number. :-D

So the process is - hook up your garden hose to the compressor. Assuming the compressor came with a carwash type spray gun, disconnect this. I needed to go buy a 3 dollar brass fitting so as to connect up the masonry spray tool to the high-pressure hose connection from which I'd just removed the carwash gun. You'll obviously need to know which size threads you're hooking up, and whether male or female, etc. Once the masonry blast tool is connected to the compressor, start the compressor, turn on the water, drop the dry hose from the masonry tool into a 5 gallon bucked of medium blasting sand. Get some goggles on of course, and assume you're going to be spreading sand all over the place...although since it's wet, it does not fly more than perhaps 10 feet or so from your project. I did mine in the back yard over grass...blew through about 5 bags (they're 40 or 50 lbs each), and the sand sort of dissappeared into the grass and dirt after a couple of rains...I did nothing by way of sand "clean up". Position yourself so as to move the tip left to right, moving from top to bottom (or vice versa) in rows as you blast perhaps a 1 foot square section at a time. You'll know how close you need to be based on what you see by way of the paint coming off of the aluminum. Once the stripping is happening, keep it moving left to right...don't stay in one spot once the paint is coming off. Not because the aluminum will get hot, but because you don't want to dig into the aluminum; once the paint is coming off, keep it moving. I did mine a section at a time until the entire hull was done...I did not have one single issue with aluminum damage, waving, anything at all. Since you're stripping the paint down to bare aluminum with a very minimal amount of surface aluminum being removed (I do mean very minimal), you won't need to scrub or treat the aluminum prior to priming, so long as you've rinsed it well and not allowed enough time to pass where oxidation begins. I would be doing this process and prime the hull the next day if possible. Once the equipment was hooked up, I'd say that it was just 2 or 3 hours of blasting work and it was done. I may have gotten it done even quicker if I'd not started out with such wimpy sand...it was barely taking anything off and took longer...then I went with medium coarse sand.

Last few tips:

Don't use playground type sand. I know it's cheap...but it's not meant for blasting at all. The right supplier will have sand ranging from very smooth to very rough. The rough stuff is best for stripping paint from bricks & masonry. Go medium and see how your paint comes off.

This process is NOT recommended if your paint is adhering well and is rather smooth. In those cases, scuff the existing paint with the proper sanding method to ready it for primer.

This process is NOT recommended when the paint on your hull will come off easily enough with aircraft engine stripper. This is a spray can product found at automotive stores, about 10 bucks per can. If your paint is rough, uneven, etc, and must come off, try first getting it off with this product via the product directions. If it does not remove it appropriately, think about the blasting method. My brother has done the blast method on several aluminum boats.

I would not recommend this process at all for wood or fiberglass boats...aluminum only.

If you've never done any kind of sand blasting or compressor painting, you should have someone with you who has. There is a technique to running the blast stream across the hull at the proper distance and movement to get the job done. I've done enough painting and blasting and understood the process well enough to have ended up with great results.

Ask any questions here, this will no doubt serve someone who wants to go this route.

 

[Jordeez98]

Re: Removing Paint From Aluminum - My thoughts

I know this thread is a couple months old. But im glad i came across it. And i've seen many others as well that deal with removing paint from hull, and restoring, polishing...I'm reading up on all of it, because as in the link in my sig shows. I'm picking up the Crestliner tonite from the father-in-law to begin the restoration process, and the first 2 things i'll be focussing on is the wood floor/transom and stripping the paint from the hull.
Right now i have NONE of the tools req'd to strip this hull so, i'm making a list and checking it twice, so i can start this project full force and hopefully have it finished by the end of the year, give or take (being my first DYI project, who knows.)

You talk about the aircraft stripper as if its the best way to go to preserve the alum. That, i think will be the way i'll go. What are thoughts on the age of the paint? This boat is i'd say late 60's and its the original paint and very weathered but the aluminum seems in fine shape..I have a pressure washer and may just give it a good cleaning and see what comes of it...then work with the aircraft stripper?
Thanks!

 

[JoeMan]

Re: Removing Paint From Aluminum - My thoughts

Sure, plus if any of the paint is loose at all, you may blow it away and make the aircraft engine stripper a bit more effective once you apply it. As for the age of the paint...my boat is a '64. The original paint was underneath another layer of something sprayed or rolled on. The original paint will always be toughest to get off, even with this product...because the OEM paint process was designed to make the paint very permanent, whereas the vast majority of DIY paint jobs don't have the environment/equipment/products to do it nearly as well.

 

[Bill in Oregon]

Re: Removing Paint From Aluminum - My thoughts

Pulling up this fine older thread as I have a '56 Crestliner Commodore to strip and repaint, leaving some sections bright.