From: "David Roden >On 7 Oct 2002 at 13:12, Sell, Ken wrote: > >> The more expensive fix would be to have the racks sand blasted >and >> re-painted. A cheaper route might be to use one of the rust >stabilizing >> products available at the local hardware store. > >I've been told that the "rust stabilizers" actually lock >moisture into the >metal and allow the corrosion to continue under the paint. Maybe >true, >maybe not, but I don't want to take the chance. I'd say either have >them >sandblasted, or spend the time with a grinder and powered wire brush. > ...
>From what I have observed, this is true. The rust stabilizers contain some kind of oxidizing agent which converts the iron oxide to the magnetite state, which is hard and black. This kind of iron oxide will not admit water, which will cause rust. At least that is the theory. In practice, especially with thermal cycling, the magnetite is microporous, and due to capillary action will soak up water when it gets wet. It will not dry as rapidly as the Fe2O3, the more familiar reddish brown rust. The retained water will cause more rust to form just beneath the microporosity. The rust has a lower density than the magnetite, and will lift the magnetite layer as it forms. No matter how hard the magnetite layer is, dp/drho at const volume is very large. The upshot is that even though the rust stabilized coupons look black, they will develop perforations (pinholes going all the way through) well before unpainted rusty steel, even if they are painted after treatment. It is quite possible if the material is protected against thermal cycling, that this treatment will work. This aspect was not tested, but these rust stabilizers must work under some conditions, or else they would not sell. __________________________________________________ Do you Yahoo!? Faith Hill - Exclusive Performances, Videos & More http://faith.yahoo.com
