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Old 11-22-2012, 07:10 PM
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dc_wright dc_wright is offline
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Mein Auto: '96 328iC, '04 325Ci
Quote:
Originally Posted by hornhospital View Post
Ever heard the expression "rust never sleeps"? It never stops, either, no matter how much clear (or other) coatings you put on top of it. That rust is continuing to eat away at the body panels.
^This^

Rust is the iron in the steel reacting with oxygen to create iron oxide. Once the process starts the surface becomes semi-porous and oxygen is entrapped there. Covering it with clear coat will deprive the process of new oxygen but it won't do anything about the entrapped oxygen so the rusting will continue until all oxygen is consumed. That may or may not be before the body panels are perforated.
There are conversion coatings that use tannic acid to convert the iron oxide to iron tannate but they're only effective on very light surface rust because they can't penetrate well to reach the entrapped oxygen areas and stop the oxidation process. In addition the conversion of the iron oxide changes it's color from brownish orange rust color to black, which defeats the whole purpose of the look.
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