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Sandblasting small aluminum parts

Posted: Fri Jun 02, 2017 12:34 am
by SolarKid
I have a few aluminum pontoon parts that have signs of crevice corrosion. My friend who owes me a favor will sand blast the parts for free. Once sand blasted, will I need to do anything else? I do not plan to paint the parts afterwards and do not mind the rough finish that the sand blasting will leave. What else will need to be done once sand blasted if anything? Can I just clean up the parts afterwords with some mild dish soap and water, maybe then submerge the parts in a bin full of water and then bake them bone dry in the sun? I plan to use 5200 on all areas between boat and parts that could trap water and cause crevice corrosion. They are small parts.

Re: Sandblasting small aluminum parts

Posted: Fri Jun 02, 2017 1:11 am
by kmorin
sun, not enough exact info to reply.

What parts, pics? what use? application? and how do they function or fit in the overall scheme? not intended as flack- but context does make a difference! Aren't you kind of asking "what's the cause of this" without any information to form an opinion? Someone may reply "what is "THIS" ?

I'm not offering a hard time, but I'm in the dark and that's from someone who's built a few aluminum boats, and repaired a few too. Just a bit too cryptic for me to even attempt a reply.

Kevin Morin
Kenai, AK

Re: Sandblasting small aluminum parts

Posted: Fri Jun 02, 2017 10:53 am
by SolarKid
Hi Kevin

My apologies. I was in a rush because my wife was nagging me. I am a long time Aluminum Alloy boat "lurker". I don't post very often but I frequently lurk in the background reading posts and learning. My hobby is fixing up old boats which are usually but not always aluminum (generally shorter than 20 ft). Call me crazy but I enjoy it.
One of my current projects is a Sun Tracker Bass Buggy pontoon.
As seen in the pics (if I can figure out how to upload them), there are some rotted wood platforms on the top front end of each pontoon. That wood will be replaced with 1/4 inch aluminum plate (already cut and ready to go). When I removed the corner brackets "for lack of a better word", I noticed some corrosion on the bottom inside of them. Unfortunately I do not have a close up picture of this but it is right where the inside of aluminum corner brackets come in contact with the aluminum hem. Note: there was no corrosion between the cleats and the corner bracket. I can purchase brand new corner brackets which are not that expensive but its more about the learning and experimenting than the money. So, having said that, my thought of having the existing ones sand blasted (for free) rather than just buying new ones is because I want to learn and see how it lasts. I do a lot of experiments on my boats just for fun. This is one as well.
My "thought" is to have them sand blasted and then proceed to any additional steps recommended by you experts and then re-mount them. I plan to through bolt them the same way they were before. In previous posts you have recommended to drill out the through bolt holes to a slightly bigger diameter and to use 5200 or other means of isolation. Lets save the type of bolt (stainless vs. hot dipped galvanized) for a different post. In addition to applying 5200 to the through bolt holes, I was also planning on applying a thin layer between the two pieces of aluminum and thus eliminating any crevices for water to get in. Keep in mind that this is a boat that will never see salt water. If you have a recommendation of something besides 5200, I am open to learning and trying it.

I also have an anchor mount (for a different boat) with zero signs of corrosion and I was going to have it sand blasted for free just because I don't like the current color of it. As far as painting aluminum goes, it seems that a substantial amount of posts on this forum all end the same way "why paint at all"? I agree.
I have had aluminum parts sand blasted in the past but they were not for boat parts. I don't mind the rough finish. I really just want to know if there are any additional steps that I should take after sand blasting.

I will attempt to upload pictures now but if they do not show up, please give me a couple of days to figure it out.

Re: Sandblasting small aluminum parts

Posted: Fri Jun 02, 2017 6:42 pm
by welder
If your Sand Blasting your parts try to make sure the media was not used on Steel as the steel particles can impregnate themselves into your aluminum and you will end up with rust spots.

Photo bucket uploads work very well here. :thumbsup:

Re: Sandblasting small aluminum parts

Posted: Tue Jun 13, 2017 12:36 am
by SolarKid
Had some complications with Photobucket but lets give this a shot. I made sure that the link was unsecured and "public". ... t=3&page=1
You might have to cut-n-paste the link into your url.

Welder, I would have never thought of that. Thank you for that advice. I'll make sure he uses new medium.

Kmorin, I'm no expert but to me this looks like crevice corrosion. It all occurs where two pieces of aluminum join together but also trap water. I am humbly making that determination as a result of what I have learned here on AAB. After looking at the end caps in more detail, it looks like the corrosion is worse than I originally thought but I don't think it has deemed the parts unsalvageable. For this "experiment", I would prefer to not use acids, most of which I cannot access anyways (besides sharkhide) which If I recall is a hydrofluoric type. Regardless, I'd like to sand blast some parts and see how they hold up over time.

Re: Sandblasting small aluminum parts

Posted: Wed Jun 14, 2017 3:53 pm
by kmorin
solar, the parts do look corroded but the depth was not clear as I couldn't get to full screen images- add blocker- and can't reflect beyond that.

I did see what looked like some fairly advanced corrosion so if the parts are adjacent and wet then you're conclusion seems valid to me?

I understand about the acid etch products being subject to regulations in different places and the straight hydrofluoric solution may well be adequate but I've little experience with it? I use Zep-a-Lume a mix of several acids and stronger in concentration that what we've seen posted about sharkhide's products.

One thing to do is put a wrench on the bracket and if you can deform it by hand- it may not stand up to traveling loads? Just a thought to give some rule of thumb of when to rebuild due to thinning from corrosion.

Kevin Morin
Kenai, AK

Re: Sandblasting small aluminum parts

Posted: Tue Aug 15, 2017 12:12 am
by alumioforte
powder coat em.