>If I have something that is rusted, I take it apart, and wire brush it
>to take off anything loose. Then I use something called Metal Prep by
>3M. It is an acid that takes the red rust that is remaining on the
>surface and does a chemical conversion of the FeO2 to Fe03. (I think
>that is the right chemistry.) The FeO3 is a tightly adhering stable form
>of black oxide. It basically kills the rust so it won't keep working
>under the paint or cold galvanizing. Then after it all dries for a a day
>or so, I paint or cold galvanize as required.
>
Steve, I believe that (if the 3M fluid is a greenish semi-clear fluid)
that it is likely to be phosphoric acid. Phosphoric acid reacts with
Ferris Oxide and turns it into Phosphoric Oxide which is black and
completely inert. It is sold at many paint stores as OSPHO. It is
relatively expensive, being about $15 a gallon, I believe, but a gallon
may be a lifetime supply. It serves as a primer and can be painted
after thorough drying. It does react mildly to galvanizing. It does
not destroy the galvanizing, tho.
Typically, Cold Galv does not require that you kill the rust before
application. It prevents further rusting. On the other hand, OSPHO
(phosphoric acid) kills the rust. An application of Cold Galvanizing
over the phosphoric oxide should weatherproof a ferrous object for
many, many years.
73, Rod
Roderick M. Fitz-Randolph
w5hvv@aeneas.net
79 Highland Hills Cove,
Jackson, TN 38305
(901) 661-9278 (Phone - after 10 AM and prior to 9 PM)
(901) 664-7539 (FAX - any time of day or night)
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