|30th August 2018, 21:32||#436|
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|The following BHPian Thanks manishalive for this useful post:|
|6th November 2018, 21:56||#438|
Join Date: Jun 2018
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Re: MPR 4142, 1959 Fiat 103D Select Restoration.
If you see paint bubbling then you can be 100% sure you will find rust underneath. You then need to sand it back to bare metal, prime and respray. As Manish said earlier, in MOST cases of respray jobs in India the painters do not understand the chemistry of painting. You are starting with steel which is not in its natural state. In its natural state it is Ferrous oxide (rust). By painting we are trying to cutoff the oxygen and moisture attacking the bare steel to create rust. Most people do not know that body filler, polyurethane primers, red oxide etc are ALL POROUS. If you apply it and leave it in the rain, it will penetrate and attack the steel below to rust it. The prep is effectively ruined so any paint on it is also ruined. There is also a bad practice to put plastic body filler direct on bare steel. This chemical reaction also traps rust under it sometimes. So what is the solution. It is to apply 2 pack epoxy primer which has zinc phosphate in it. It must be sprayed on AFTER the metal tinkering is complete, and the body washed down with warm soap water to neutralise the acid in the welding, and then heat dried either in a booth or in the sun. The epoxy cures hard in 2 days completely. It is rock hard and imporous. After this there is no chance you will get surface rust. All body filler is put on this surface. On top of this primer, basecoat and clear lacquer. Clear lacquer is what protects the paint. I put on 4 coats. 2 on, then flat. Then another 2 on, then flat and polish. Hope this helps.
On a separate note. Quality respray is only possible in a paint booth with dust extractor and 60deg heat for 90mins. Sadly almost no one paints in a booth in India. Also clear over basecoat is far better than two pack when it comes to a glass like finish.
Best wishes. Sarajit