msportwagon

I was inspecting my front subframe components and noticed surface corrosion (white flaky residue) and seems a lot of moisture is trapped between the belly pan and the bottom of the subframe. Is this normal?

donpb

If your car is running fine, I wouldn't worry about it. If its appearance bothers you, wash it off and see if it reappears.

gman6262

What I've noticed with my car is that anywhere you have dissimilar metals in contact - aluminum and steel - that's where you'll have the greatest rate / risk of corrosion. e.g. aluminum heat shields attached to the steel body floor, aluminum subframe stiffener attached to the steel subframe, steel subframe attached to the aluminum front frame clip, etc. My strategy since I plan to keep my car is to use zinc anti-sieze and cold galvanizing spray (which is a zinc compound) anywhere there's a joint between the aluminum and steel, and zinc anti-sieze on all steel hardware. The zinc becomes sacrificial instead of the aluminum, and this should offer some measure of protection. I'm also using fluid film to touch up any steel parts and hardware prone to corrosion around the front and rear suspension, and the rear subframe attachments to the body. I live in Montreal, my 535 is my daily winter driver, and we deal with horrendous amounts of salt on the road five months of the year.

msportwagon

thank you. Everything works fine. The bi-metal construction issue definitely seems to have merit. Coating the surfaces with those compounds makes sense also. I actually sprayed some leftover Gemplers rust converter for now. I should wash and clean all those surfaces and redo with what you suggested.