Cleaning aluminium corosion

I have an aluminium casting which sits in saltwater as part of a beaching leg. It is only occasionally used but has suffered from corrosion under the painted finish.

Before I can use a primer and topcoat paint system I need to clean off the white powdery corrosion products. Some parts of the casting are difficult to get to with a rotary wire brush and ideally I would like to chemically remove the corrosion products rather than have them blasted.

Has anyone any experience of doing this?

Many thanks in advance.

Haven't had any experience of this problem, but for future ref could you not attach a zinc bar/plate as sacrificial anode as on ships hulls ?

George.

It hasn't stopped corrosion on my ally outboard leg when the paint is breached. Anodes only prevent galvanic corrosion this corrosion appears to be different.

Hi Steve

Use caustic soda solution to clean the part. Rinse thoroughly. Make sure it is perfectly dry before using an etching primer. Then carry out the remedial paint job.

regards

You might find a lump of Magnesium bolted on somewhere close to your inaccessible area won't do any harm.

Salt water ,Aluminium , not good.

You might find a lump of Magnesium bolted on somewhere close to your inaccessible area won't do any harm.

Salt water ,Aluminium , not good.

Caustic soda is highly aggressive to aluminium and very difficult to neutralise. Srcubbing with phosphoric acid works but you need to neutralise it with a baking sod solution afterwards.

Having had a few decades repairing, building, maintaining and inspecting aircraft, usually made of aluminium alloys I know how difficult it is to minimize corrosion where they are exposed to seawater, i.e some helicopters and floatplanes. All corrosion products must​ be removed before renewing the protective surface which must​ be cleaned, dried,inspected and repaired frequently. You might find this helpful http://ebushpilot.com/seasalt.htm​

Trevor

The Dornier they recovered from the sea a while ago was going to be cleaned with a citric acid based solution but I don't know how they intend to neutralise things once it is clean.

Mike

Edited By Mike Poole on 03/03/2018 21:12:54

I would avoid using chemicals for removing corrosion, remove it mechanicaly by grinding and make sure all traces are gone. If you have access to chromic acid you can anodize the part, follow with etch primer and top coat.