Gord: If you remove the black/blue surface oxide from the backside of the welds, and if the welds are of good quality and free of slag, etc., the welded areas should exhibit similar corrosion resistance as that of the base metal. Under those conditions, a supplementary coating should not be required. Understand that, depending on the specific atmospheric conditions, i.e., heavy industrial, marine, etc. pitting corrosion of the base metal may occur, if not kept free of atmospheric deposits. Hope this helps! David Hendrix The Hendrix Group Inc.