What is galvanic corrosion on a car?
Corrosion that starts exactly where a bolt, bracket, clip or panel joint touches the body is galvanic. When two different metals touch and get wet, the weaker metal corrodes. Steel touching aluminium is a common case. That is why the corrosion traces a fixing rather than a patch where water sat.
What kind of repair does it need?
Removing the fixing, cleaning both surfaces to sound metal, and separating the two metals so they no longer touch. Then priming and painting. Fixing the paint without separating the metals means it comes back in the same spot.
Painting without separating the two metals means the corrosion comes back in the same spot. Ask what they will use to keep them apart.
What to do next
Tell the shop the corrosion is at a fixing and needs isolating, not just painting. Ask what they will use: an insulating washer, tape or a sealer are normal answers. Check wherever an accessory like a bull bar, roof rack or towbar is bolted on.
Sources
- Aluminum Associationindustry association
Galvanic corrosion occurs when a metal is in contact with a dissimilar metal…
- Axaltapaint maker
phosphoric acid wash primer (etch-…
- PPG GBpaint maker
treat the surface with the correct metal treatment fluids and etch primer…
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