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Seeking a temporary, easy-to-remove rust inhibitor for mild steel

April 30, 2012

Q. I've learned a lot from reading through this forum, but haven't found a solution to the particular problem at hand.

I weld together various pieces of mild steel for hobby and volunteer projects using both TIG and SMAW process. Prepping the steel for SMAW is simple, "stick" welding works fine with just simple sanding of the area to be welded. For parts to be TIG welded, though, I like the surface to be free of most oils and chemicals.

My favorite cleaning prep for TIG welding is sandblasting, because it's fast and effective, and because I don't like the smell of solvent based cleaners. (In my earlier years I worked with lots of chlorinated solvents, and I now hate using anything with a strong smell that isn't dinner.) It's also a great prep for painting after welding.

The problem is, there is usually a time lapse between sandblasting and welding. I'd like to be able to store sandblasted parts, indoors, for a few months at average northeast US humidity, without having lots of surface rust. (The sandblasting is new commercial aluminum oxide media.) I could paint the parts, but then I would have to clean the paint off before welding, which kills the advantage of sandblasting. The same applies to any oils or rust preservers that I know of.

Is there a short term, preferably water soluble and non-toxic, coating that I could put on the steel to protect it in short term storage? I know they make "weld through" primers, but they aren't designed for the TIG process. The parts will eventually be painted, so although I could weld through light oils, I'd like to avoid a solvent based cleaning step. Any thoughts or ideas would be greatly appreciated.

Oh - part sizes are anywhere from 2" square to 2x6 feet, usually A36 alloy, welded with 70S2 rod, and usually painted with spray cans. The projects vary, but a typical example would be brackets to hold an antenna on the roof of a trailer or shed.

Tom Smith
- Albany, New York

June 27, 2012

A. Hi Tom,

Your requirement could be addressed with proper material handling and Volatile Corrosive Inhibitor emitter disks sold by some packaging vendors. VCI emitter disks fill an enclosed space with a vapor which condenses on metal and protects against rust, but take the part out an hour or two before welding and any surface contamination will have evaporated off. Use of this will require an enclosed material storage area and you will have to calculate how many disks will be needed based on the manufacturers recommended volume of protection.


Stuart Grant
- Mount Clemens, Michigan, USA

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