Matte finish on aluminum?

Hello all. Here's my first post.

A little backstory. I bought a 1991 18ft smokercraft pro alaskan last fall. I started out this spring planning to put a new coat of paint on her before fishing this summer. That lead to noticing the deck was a little soft, which lead to finding the foam was a little waterlogged, which lead to finding countless spots where the corrosion was so bad that I could poke holes in the hull with my finger. It looked fine from the outside, but she was pretty shot from the inside. I'm still not sure what I'm doing with that boat as the aluminum is pretty thin to consider welding (riveted boat) and a lot of the holes are near or through riveted seams or riveted internal ribs. I might try jb weld someday. Too bad I stripped the paint and started polishing her before I discovered the corrosion holes.

In my eagerness to still be able to make the camping/fishing trips I had planned I ended up buying another new to me tin boat. This time I went for broke (by my standards) and bought a 2001 North River Mariner, 20ft, with a Merc XR6 150.

So that brings me to this post. The new boat is great, but has some small scallop shell-shaped external corrosion spots. They are slight enough that I can't feel them with my finger, but also significant enough that just an acid wash and 3M polish won't take them off. I've had some good results going from acid wash to 1000 grit to 2000 grit wet sanding, followed polishing with a DA polisher. However, I'm not the biggest fan of the shiny mirror finish. It's a lot better than it was (especially since the previous owner tried to spot polish the corrosion spots which left shiny leopard spots all over the boat). Still though, I would prefer more of a matte finish before I hit it with shark hide.

I have seen suggestions ranging from using a palm sander with 400 grit and WD40 to blasting with sand or walnut. Blasting would be problematic because I borrow shop space and can't make too much of a mess. A brushed look would be cool but I can't see a good way to keep my lines parallel, especially with the curvature of the bow. I haven't been able to find any good videos on a blasted finish because most videos about blasting tin boats are about stripping paint.

Here you can see what I mean by the previous owner tried to polish these spots off. Now imagine this times 100. Not sure why you would keep going when it clearly wasn't working.

For what it's worth, I have vintage factory brochures from both Alumacraft and Feather Craft that recommends the maintanance of their finishes with regular steel wool by hand.

Personally, I don't like the idea of embedding micro pieces of dissimilar metals in the aluminum and have instead tried the red scotch brite pads in a similar fashion with mixed results. It leaves a satin finish but is not nearly aggressive enough by hand.
However, I have seen favorable results done by cutting the scotch brite pads to fit a DA. It leaves a swirled finish, though.
I've also recently ordered Aluminum Wool off of Amazon but have yet to try it out.

Just a couple of ideas to ponder.

mbullen said:

For what it's worth, I have vintage factory brochures from both Alumacraft and Feather Craft that recommends the maintanance of their finishes with regular steel wool by hand.

Personally, I don't like the idea of embedding micro pieces of dissimilar metals in the aluminum and have instead tried the red scotch brite pads in a similar fashion with mixed results. It leaves a satin finish but is not nearly aggressive enough by hand.
However, I have seen favorable results done by cutting the scotch brite pads to fit a DA. It leaves a swirled finish, though.
I've also recently ordered Aluminum Wool off of Amazon but have yet to try it out.

Just a couple of ideas to ponder.

Click to expand...

Yeah, I've seen a lot of warnings about micro particles of steel getting embedded and then corroding.

Someone suggested trying Bio Kleen as it leaves a milky white finish. I gave it a try on my junk boat and it does leave a white finish but that isn't really what I was looking for. It just looks like I dusted my boat with white chalk. It also isn't all that uniform.

I'm increasingly thinking I'm just going to end up with a shiny finish covered by shark hide.

Aluminum oxidized naturally as a way of protecting itself. When we remove that oxidizing, we are also removing some of the aluminum and over time by repeating this process we make it thinner. While not pretty, it has been recommended by aluminum mfgrs to leave the oxidizing alone, or clear coat or paint the surface to keep it from oxidizing. You will find many old aluminum hulls that have that dull old ugly finnish that is actually slowing down/ stopping the removal of the aluminum. I choose a painted hull for appearance, but my Islanders is natural below the waterline. Ugly yes, but no sign of any corrosion or loss of material from removing the oxidizing.

OregonApe said:

Yeah, I've seen a lot of warnings about micro particles of steel getting embedded and then corroding.

Someone suggested trying Bio Kleen as it leaves a milky white finish. I gave it a try on my junk boat and it does leave a white finish but that isn't really what I was looking for. It just looks like I dusted my boat with white chalk. It also isn't all that uniform.

I'm increasingly thinking I'm just going to end up with a shiny finish covered by shark hide.

Click to expand...

I’m curious if you found a solution. I have an 18’ Mariner with the same type of corrosion or wear. I’m not sure if it’s a type of salt corrosion or just road damage from little bits of gravel, etc.