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Stainless Steel "rust" marks on paint
On Tue, 27 Mar 2007 06:52:12 +1000, Peter Hendra
wrote: On Tue, 27 Mar 2007 20:51:00 +1200, Eric Stevens wrote: On Mon, 26 Mar 2007 17:56:36 GMT, "Gordon Wedman" wrote: "Peter Hendra" wrote in message ... On Sat, 24 Mar 2007 12:44:13 GMT, Rich Hampel wrote: Probability is that the welds are not ground flat and smooth and crevice corrosion is underway in the 'intersticies' of the weldment (poor weld technique ... not a full penetration weld). To be 'corrosion resistant' (chlorides, etc. attack stainless) all the weld must be flat /smooth by grinding and then polishing/buffing to a high mechanical mirror polish. Any 'weld-lap' or pin-hole in the weld will be a source of 'rust' .... gotta be closed and then smoothed. . This has just made sense as only one of the bolt on "feet" for the ladder suffers from the problem. I'll try it. Thanks very much to all who responded. regards Peter Hendra A friend has gone thru this with his stainless. People at his workplace that know about his sort of thing told him he needed to passivate the welds. They gave him some solution to paint on the welds. I believe this is hydrofluoric acid, perhaps a mixture with other acids. Requires very carefull application. It took away the surface shine. Don't recall the final result but I can ask him. It won't be Hydrofluoric Acid, which is one of the nastiest nasty chemicals on the face of this earth. It's much more likely to be a 50~50 mixture of Hydrochloric and Nitric acids plus, sometimes, a little Phosphoric acid. You should somewhere find an expert and read http://www.assda.asn.au/asp/index.asp?pgid=17982 Whatever you do, you don't want a strong brew and you should let time be your friend. Eric Stevens Thanks Eric, A great site and I love your phrase "let time be your friend" - poetic. May I have your permission to use it in future - yes, I'll cite you as the originator? I don't want to get flamed. Feel free to use it. :-) I was really trying to say use a longer exposure to a weak brew and don't use a concentrated mix just to get a quick result. Eric Stevens |
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