Acid Dipping

Q: Acid Dipping

I’m considering having my front subframe dipped to remove the old paint etc. The procedure is one type of acid to remove paint and grease followed by hydrochloric to remove rust (there is only a very small amount).

A: One draw back to acid dipping is that if the clean-up isn’t thorough, traces can bleed through the paint and cause blistering or rusting, as Tom Sexton reports. Items with hidden nooks or pockets where the acid cannot be cleaned off adaquately can hold the acid, to come out later. Also, these hidden areas now have no paint or crud to protect the metal from rust since you cannot get paint into areas you cannot see. On thin sheetmetal parts like hoods, or body shells, this is a particular worry. The phosphate dip will probably not provide enough protection in the long run, especially in humid regions, or if the car is exposed to frequent rain or snow.

On my car, I scraped off the grease, dirt, and flaking paint with a paint scraper and cleaned using a degreaser. Then I used a heavy wire wheel on an angle grinder to get the more stubborn paint and surface rust off my subframe (off the car).

One advantage to this time consuming process was that I could then grind or chisel off the welding slag and other blemishes. It’s amazing how sloppy the factory was. I spent several hours over a number of days preping the subframe.

A: I had mine acid dipped years ago. Mine came out great and has never had a problem with leaching of the acid. I did a couple of things to prevent this. First, I washed the frame with soap and water when I got it back. After a long rinse, I blew it dry with compressed air. Then I sprayed the whole frame with lacquer thinner and again air dried it. I then primed it. no problemo!!!

I applied POR-15 to all accessable areas, even inside the boxed fram area, as far as I could reach. There were areas I knew would not be covered, but then I didn’t grind down to bare metal there either.

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