Aluminum Boat Windows -- Re-anodize, clearcoat, or paint?

A. Anodizing aluminum comes from dipping in acid and the surface is oxidized. The oxidized surface is much harder than bare aluminum. Its unusual to paint an anodized surface because dyes can be added to the acid bath to make a colored finish. As long as you don't scratch the surface the anodized coating is ok. I'm sure some chemicals will attack the coating. If the anodizing is removed the aluminum tends to wear off on your hands leaving gray imbedded in skin.

Thanks for the advice, Jim. I checked it with a voltmeter - the aluminum isn't conductive, which I guess shows that it is still anodized. There are a few minor scratches, but I can live with them. So on the assumption that the scratches won't cause problems in the future, I think I'll leave the frames as is.

Caution! Hi Ross. Methylene chloride aircraft stripper is harmless to most if not all metals. If there was anodizing on these frames, you didn't hurt it. But it is environmentally unfriendly, really noxious stuff -- it demands rubber gloves [on eBay or Amazon], goggles [on eBay or Amazon], and working outside and upwind for good ventilation.

Regards,

A. Of course they can be re-anodized.. They are aluminum! However you may not be as pleased with the rework as you were with the original finish. It just depends on the oxidation that they have been subjected to, as well as the overall looks of the part in its current state.

You can take the part to a plating shop and they should be able to tell you what to expect more accurately than I could here without seeing the part myself.

You will need to strip the old plating off of the surface in a Nitric based stripper or other acid based stripper and prep the surface as you would in any other situation.

Make sure you do not etch the part as the silicates in the casting will become more exposed and will cause the plating to look undesirable.

Good luck with your task.!

A. You can try 5% ammonium citrate solution,pH must be 7-8. Dissolve 50 gm citric acid in 1 lit water and add ammonia [on eBay or Amazon] until pH is 7-8.Your parts are probably anodized and best solution is to find nearest anodizing shop.Hope it helps and good luck!

A. Sanding those frames will probably get you in even more trouble. The previous response was correct in stating that they are anodized, they look like raw metal but aluminum frames will almost always be anodized. Read some articles about the process and you will see what I mean. There are many hobbyists that do their own anodizing but the process is a bit nasty. If there is a lot of pitting you may consider anodizing them with a matte finish. The strips that hold in the glass may not be salvageable and you will have to find a glazier supply that carries them. There are lots of anodizing places around and it is not that expensive to get it done except if your parts exceed the vat size. Also check into Cerakote, a ceramic finish used to coat all kinds of metals and has good corrosion inhibition.

A. Unfortunately even if you use SS screws, once the screws are tightened, the anodized seal around the screw is broken. With time, corrosion will begin to occur in these areas again. Good luck with your project.

A. Hi Holly. I think you're closer. I wouldn't sandblast it or acid wash it, but would try either Mother's Polish or another specialty cleaner/polish. It may take more than a "wash" though; you might need to use the aluminum polish on a buffing pad in an electric drill for really good results. Best of luck.

Regards,

A. Holly,
I often get sent a part with a "spot that won't wash off" only to determine that the surface has been physically damaged by etching.

A good analogy for this is wood. If you spill something on your wood table, you can wipe it up. If you hit it with a hammer, you now have a dent that can only be fixed by sanding it out. The deeper that dent is, the more you have to sand to get rid of it.

Metal is much the same. When the surface is etched or pitted, the deeper the damage goes, the more work it is to polish down through it. As with sandpaper on wood, you typically start with the coarser stuff and work your way down to the finer stuff. Sandblasting would be at the far end of the "coarser stuff" in this case. If the condition of the surface is bad enough to warrant that and you have the equipment for it, it's probably the faster and easier method. From the photos, I'm guessing it's not that bad, though.