Ned Simmons wrote in news: snipped-for-privacy@news.suscom-maine.net:
I have spent my career in part designing instruments and structures to go into the ocean. If you put welded 304 in salt water without post welding heat treatment or pickling there will be crevice corrosion around the weld and it will fail. Even 304L is dicey, although first world 304 and 304L now have much better carbon content control than they did in the 60s when I started. Even the marine dominated environment, say 1000 ft from the shore, commonly will cause serious corrosion problems on parts welded without careful attention to heat control. We have some buildings here on the beach with architectural elements made out of welded 304 that are ugly with bleeding corrosion from the welds. It is an example of bad welding practice and a lack of understanding of the limitations of stainless in sharp relief. Manufacturers of marine hardware, like sail boat fittings, go to great lengths to design welding procedures and post welding finishing treatments to eliminate corrosion problems. If you're in the desert, on the other hand, there is no problem with 304 corrosion unless you're down wind of the wrong factory's smoke stack.