RE: MIC on Potable Water Piping.

>To quote nalco " the most likely cause
>for this perforation is microbiologically influenced corrosion involving
>acid producing bacteria". sample of the potable water indicated a 15 ppm
>choloride.

That much chloride will really do a number on stainless, regardless of whether it was micro-biological or other contamination contamination. The HAZ cracking you describe also sounds very much like sensitization--chromium carbide precipitation due to weld heat. You might want to check the carbon levels in the steel you're using. If it is sensitization, you're in deep sauce if you have a relatively high carbon content. Some years ago there were some nuke plants here in the US that had to have large quantities of pipe replaced because the weld HAZ material was simply disappearing. Re-welding didn't help much because the heat just tied up more chromium. I've seen this is some hard ballast tanks made of stainless steel used in nothing more corrosive than sea water.

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)