Guest 51c8Joe Posted September 28, 2013 Share Posted September 28, 2013 The data plate on my 35 Pontiac had been painted with at least three coats of paint.I removed the plate and put it in an acetone bath overnight. The paint came off easily, but the acetone appears to have left a uniform light grey coating on the plate. The back of the plate was bright and shiny before the bath, but now is grey. Supposedly acetone does not react with aluminum, but something sure did. I had used the bath container before and it may have had some engine oil residue when I added acetone. The grey coat can be removed with steel wool, but takes a lot of scrubbing. Any ideas on what happened and what may remove the coating? Thanks for your help. Joe Link to comment Share on other sites More sharing options...
Guest Commodore Posted September 28, 2013 Share Posted September 28, 2013 I found this answer on the web which might explain what you saw."Pure acetone cannot corrode aluminum or other metals. However, technical grades of acetone could possibly have acidic, or basic impurities impurities that might attack aluminum Al is attacked for instance by HCl to form AlCl3, but NaOH also attacks it to form NaAlO2. Both reactions produce hydorgen". Link to comment Share on other sites More sharing options...
Guest 51c8Joe Posted September 29, 2013 Share Posted September 29, 2013 Thank you Commodore for your response. I guess I had something in the can I used for the bath. I'll know better next time. Back to the steel wool and polish. Joe Link to comment Share on other sites More sharing options...
hddennis Posted September 29, 2013 Share Posted September 29, 2013 Not sure in this case but I seem to remember reading some of these data plates are made of zinc, maybe that's why the reaction?Howard Dennis Link to comment Share on other sites More sharing options...
Guest 51c8Joe Posted September 29, 2013 Share Posted September 29, 2013 AHA! That is the most likely explanation. I'll try to polish this one out, or else find a repro source. Thank you for your help. Joe Link to comment Share on other sites More sharing options...
Guest QGolden Posted October 3, 2013 Share Posted October 3, 2013 Yes, if you can see the stamping from the back side the plate is made from a zinc alloy, the aluminum would crack if stamped that thin and sharp. The zinc alloy is softer, but a sacrificial element, so it needs to be coated anywhere where it makes a steel contact. The body is painted under the plate and the rivets are brass, so no direct steel contact. Link to comment Share on other sites More sharing options...
Guest 51c8Joe Posted October 3, 2013 Share Posted October 3, 2013 Yep, it's zinc, and short of spending my remaining years trying to polish of the grey residue I'll have a repro made. A. G. Backeast can make or repair just about any tags or plates. Link to comment Share on other sites More sharing options...
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