Galvanic Corrosion

[BlueMax]

My car is a 2002 SV. I started having blisters popping up on the rear aluminum panel in the area of spare tire. Has anyone had this issue, and if so what did you do to solve the problem.

[NVP66S]

Any copper or brass nearby?

Edited November 5, 2014 by NVP66S

[BlueMax]

No, on brass or copper in the general area, maybe 15 feet away I have some copper tubing. Blisters started last year, treated by sanding and brushing with new stainless steel brush and then epoxy primer then paint/clear coat. Paint supplier said that epoxy would work better than zinc chrome-mate?

[coffee break]

How much water has the car been exposed to, and are you in an area that uses road chemicals?

[BlueMax]

Car only has 500 miles on it and is a garage queen. It;s only been wash twice, never seen a rain drop..

[Warren Nethercote]

If you have some poor grounds in that area (tail or licence plate lights?) you may have stray currents 'roaming about' looking for a better ground. Any electrical systems performing oddly? I have had similar experiences in a marine environment with blistering caused by galvanic action and in that case epoxy primers performed worse than traditional primers. The real solution lay in finding the source of the currents, whether electrical or galvanic.

[NVP66S]

  BlueMax said:

No, on brass or copper in the general area, maybe 15 feet away I have some copper tubing. Blisters started last year, treated by sanding and brushing with new stainless steel brush and then epoxy primer then paint/clear coat. Paint supplier said that epoxy would work better than zinc chrome-mate?

 

Zinc Chromate is an excellent primer for aluminum. Sticks well and good at corrosion protection. It's getting hard to fine because the EPA hates it for good reason. Very toxic if you eat it. Sounds like it's not galvanic corrosion.

Dan

[slomove]

I know Magnus Feuer (administrator of the California Caterham Club web forum) had the same thing with his SV of similar vintage. Might have been a manufacturing flaw, maybe insufficient etching of the aluminum.

[BlueMax]

I guess it’s possible that I have a partial grounding issue, but all the lights are functioning well? I could remove the grounding wires and clean and reattach just as a preventive precaution. I know Ford had issues with the Mustang hood due to contamination of iron oxide causing blistering. Maybe my car was poorly prep at factory in this area causing the corrosion? I would like to chat with Magnus about his issues and resolutions!

[Manshoon11]

Inadequate grounding can cause very severe corrosion damage.

 

You should share a picture. Might be atmospheric corrosion still....... but hard to believe it'd be crevice corrosion.

[jlumba81]

If its caused by a bad ground, can't you just disconnect the battery when its being stored?

[BlueMax]

That thought was running through my mind last night. My car has the master kill switch on LH side of bulkhead so all voltage is off?

[Manshoon11]

That isn't a good answer.