Corrosion on aluminum with pics

[jtrom]

After stripping the paint off my boat, I noticed this corrosion. What is the best way to get rid of it????...scotch brite does nothing

 

[rwhodel]

Re: Corrosion on aluminum with pics

On my boat, I scrapped out the inner transom piece because of aluminum corrosion and fabricated a new piece. For the outer hull where I had corrosion, I sanded with a Makita sander with 120 grit sandpaper and painted with a rust/corrosion resistant paint.

 

[Mojo^]

Re: Corrosion on aluminum with pics

I had a lot of that galvanic corrosion on my boat. I sanded with a DeWalt orbital finishing sander with 60 grit sandpaper, sprayed with a 50/50 mix of water and white vinager scrubbing with a stainless steel pad (ChoreBoy) and final cleaned with a product called AlumaPrep with Scotch-Brite pad before applying Rustoleum self-etching primer. It seems to have worked just fine. All of this needs to be done just before you are ready to apply primer.

 

[Yacht Dr.]

Re: Corrosion on aluminum with pics

Alumiprep is very good at cleaning Alum .. get the chunkies off first.

60 grit IMHO is a little too abrasive .. 120 meh.. I like 220 .. then wash/dry/AP it and then prime ..

There is a sticky up top on the How To thread that gives you some info.

Oh yea.. I personally would not use SS and Alum together. However please read my sig ..

YD.

 

[kfa4303]

Re: Corrosion on aluminum with pics

HI Dr. I understand why you don't want to have contact between dissimilar metals, but what else can/should be used? Is a good coating of 5200 on SS fasteners not enough to prevent electrolysis? Just curious. Thanks.

 

[orlandoclippertim]

Re: Corrosion on aluminum with pics

I am doing LOTS of that on my boat now. I started with scotchbrite rolock disks. They lasted about 2 minuites and didn't do much area. Then I FOUNd THE CURE ! Norton abrasives makes a paint stripping disk that fits your angle grinder. It comes in 4-1/2 inch and the bigger size too. It is about 1 inch thick and quite firm. Blue in color. I can do about 15 square feet easily before it is worn down. It does leave a coarse texture behing and it is agressive ! I have tried comming behind it with a green scotchbrite wheel and then scotchbrite + alumiprep by hand and that clears up the roughness and makes ready for use or polishing. The big norton wheels
work GREAT ! Got mine at HD.

Tim
ps is that a lone star or alumacraft ?

 

[boatnut74]

Re: Corrosion on aluminum with pics

I got the same thing going on with mine. I thought about soda blasting the affected areas but havn't decided yet.

 

[jigngrub]

Re: Corrosion on aluminum with pics

These Scotch-brite Surface Conditioning pads will make short work of that stuff.

Try the maroon first and if that one isn't quick enough switch to the brown. The maroon removes paint and carpet glue quicker than anything I've ever used.

 

[boatnut74]

Re: Corrosion on aluminum with pics

Alumiprep is very good at cleaning Alum .. get the chunkies off first.

60 grit IMHO is a little too abrasive .. 120 meh.. I like 220 .. then wash/dry/AP it and then prime ..

There is a sticky up top on the How To thread that gives you some info.

Oh yea.. I personally would not use SS and Alum together. However please read my sig ..

YD.

Alumiprep basically neutrilizes the corrosion correct?

 

[Yacht Dr.]

Re: Corrosion on aluminum with pics

Alumiprep basically neutrilizes the corrosion correct?

Alumiprep removes the corrosion and surface contaminates. It is used in a multi-step process that needs to be done at one time. You cant just AP it and let it sit over night or the corrosion can start again microscopic.

But yea.. it Basically neutralizes it ..

YD.

PS. you have to remove the bulk of the corrosion by mechanical means first .. like those surfacing pads stated above work great ( you can get them in a rol-lock 2" or 3" for a right angle air grinder also ) .

 

[sschefer]

Re: Corrosion on aluminum with pics

Clean it to bright white mechanically, wash with soap and warm water, dry, alumaprep, let set for 15 minutes, rinse, wash with warm soapy water and let it stand in the open air. It will start to re-oxidize in about 2 secs but it will take about a week to create a good corrosion preventing, natural layer of oxidation. Bright shiny aluminum is not good when mixed with water, oxidized aluminum is what you want.