Metal Finishing

[Tafflad]

Hope it's not off topic ... the 'technical forum' seems to be discussing drugs, guns and not much to do with boating.

I use (with my boat) on salt water, a towed sports item .. a SkySki.
http://i771.photobucket.com/albums/xx351/Tafflad/boats%20n%20things/SkySki.jpg

The seat post ... is a powder coated aluminium item ... fairly thick cast section.
However powder coating ... and saltwater does not seem a good mix ... where there are though holes water has obviously got under powder coat and it is coming off in big pieces.

I had the wings anodized ... but had to mirror finish polish first
http://i771.photobucket.com/albums/xx351/Tafflad/boats%20n%20things/red.jpg........ and colour fades in a couple of uses, so think anodizing the seat frame is not a good idea.

If I sandblasted or chemically removed the powder coat .... what should I put on as a good finish ........ maybe an acid etch high build primer and some form of good marine paint (2 part epoxy perhaps ?)

What paint finishes work best with saltwater. ?

 

[bruceb58]

Re: Metal Finishing

Hope it's not off topic ... the 'technical forum' seems to be discussing drugs, guns and not much to do with boating.

Are you referring to the NON Boating technical forum?

If you get a chip, no matter what the coating, you will get corrosion under it and that includes any paint. The thing you have to do is touch up when you get a chip to keep the corrosion from starting in the first place. Your idea of a primer followed by a quality paint sounds good.

 

[dingbat]

Re: Metal Finishing

As noted above, the problem is not the coating, it?s the chipping. We used 2 part epoxy paints in the past and now power coat with very good results around acid solutions and corrosive waters that makes saltwater seem like baby oil. The only permanent solution is to make the product out of a non-reactive material like carbon fiber or stainless steel

 

[Tafflad]

Re: Metal Finishing

The issue is this is not chipping the outer surface is unmarked ... this is I guess water getting behind the powder coat ...it spreads into large areas, before it breaks at some point and lifts.
No damage to outer skin.

I assume that at holes ... there is some damage .. and water is getting behind the powder coat and spreading ... causing layer to lift.
Probably not a good adhesion to metal in first place.
Hence thought an acid etch primer that bonds with ally may be better ... as long as I can get a paint that will bond with primer.

 

[bruceb58]

Re: Metal Finishing

Possible that, at a hole, the powder coating didn't properly get coated within the hole and obviously it's not going to be inside the metal piece either which is also a problem with moisture getting under the coating. Sounds like a problem you will have no matter what you paint with though. Bottom line...salt water environment is a pain in the butt.

 

[robert graham]

Re: Metal Finishing

Hope it's not off topic ... the 'technical forum' seems to be discussing drugs, guns and not much to do with boating.

I use (with my boat) on salt water, a towed sports item .. a SkySki.
http://i771.photobucket.com/albums/xx351/Tafflad/boats%20n%20things/SkySki.jpg

The seat post ... is a powder coated aluminium item ... fairly thick cast section.
However powder coating ... and saltwater does not seem a good mix ... where there are though holes water has obviously got under powder coat and it is coming off in big pieces.

I had the wings anodized ... but had to mirror finish polish first
http://i771.photobucket.com/albums/xx351/Tafflad/boats%20n%20things/red.jpg........ and colour fades in a couple of uses, so think anodizing the seat frame is not a good idea.

If I sandblasted or chemically removed the powder coat .... what should I put on as a good finish ........ maybe an acid etch high build primer and some form of good marine paint (2 part epoxy perhaps ?)

What paint finishes work best with saltwater. ?

Raw cast aluminum will oxidize and turn grey/white(like an aluminum propeller). I expect your powder coating was applied mostly for looks and now it's bond with the aluminum has failed and it's a problem. Maybe you should just remove all the powder coating, sand or wire brush the aluminum and let it "weather" naturally, a grey/white color? White, chaulky aluminum oxides can be removed with a mild acid, if required. Good Luck!

 

[NSBCraig]

Re: Metal Finishing

Powdercoat holds up to salt better than anything else, if it failed it was most likely from improper prep. A little oil in the hole from drilling lube will cause this.

 

[Tafflad]

Re: Metal Finishing

So you think I would be best to clean it all off and get it re-powder coated .... is there any particular spec for marine use

 

[robert graham]

Re: Metal Finishing

You could strip it, polish/buff for the finish you like, then spray a coat of clear polyurethane on it to seal it up. Thereafter, sand and touch-up as required.

 

[NSBCraig]

Re: Metal Finishing

Yeah there are specific powders made for marine use. I haven't work in it for ten years so I'd start by talking to some shops near you.

 

[zagger]

Re: Metal Finishing

Strip and re powder coat. Before re powder coating make sure to file small radius on all sharp edges. The sharp corners will produce the thinest coat and give a foot hold for any oxidation. Also apply a epoxy paint barrier anywhere two metals are fastened together to prevent electrolysis. Powder coating will give you best protection against elements if properly prepped.