Source for PREN > 27

Yes.

'All' is a big word. What's the application, a structure made of mostly stainless steel or a product containing stainless steel parts?

This could be either simple (good quality stainless of a certain grade will always meet the requirements) through to impossible (no data available on a stainless steel tube incorporated in a critical component of a larger product needed for the job).

Stainless steel 304 and 316 grades are very common. Why not just use those grades from a reputable supplier to show compliance? Unless the stainless steel is being used for a very special chemical process I don't see this specification being any more than a rephrasing of the statement "low grade stainless steels must not be used".

Thanks, I realize 304 and 316 are common grades but their PREN values are too low, they are 18.1 and 24.1 respectively: The Pitting Resistance Equivalent Number (PREN) is a measure of the relative pitting corrosion resistance of stainless steel in a chloride-containing environment. Higher PREN values indicate greater corrosion resistance. The formula for PREN is: PREN = %Cr + 3.3*%Mo + 16*%N

Have you tried searching right here on IEEC Globalspec?

Yes, it turns out that Molybdenum, especially as molybdate ion is highly effective as an anodic corrosion inhibitor. Incorporating this into the metal will tend to localize any pits to the points on the surface that are higher in Mo, and oxidation of Mo will nail it down and clog the anode worse than a case of government cheese.

Without prying too much into your business, why not just order all this stuff in the Ferritic "SEA CURE" grade? It has a PREN value much higher than 27.

Good luck, sorry I do not have the source on this, but I used to order things like pipe fittings in CN7M from Warren Metals, Inc., in Houston area.

Thanks James, I never heard of that stuff before. I looked it up on line and calculated the PREN to be 35.54 on the low side of the specs. But one issue I see is they recommend GTA for welding and that is not practical for our shop set up and these are big structures, kind of, they are big frames about 18' wide and 54' long. That is a lot of TIG welding. But Thanks!

PREN = Cr + 3.3(Mo +0.5W) + 16N

The nearest AISI grade is shown, where appropriate, otherwise a typical trade name used by some of manufacturers is shown.

NS - Not specified

1 Typical composition only available

2 The “superduplex” steels in particular are subject to tighter restrictions on PREN than that implied by the minimum composition of the EN grade. For example, the equivalent ASTM grade or the specifications of the oil and gas industry e.g. NORSOK or NACE typically require a minimum of PREN =40.