Dear Sir, We have a product, drawing specifies the material is SUS304. The product is a swimming pool cleaner. It contacts swimming pool water (contains of chloride). The stainless steel does not need to suffer any compression or tensile stress during operation. After one year, we get complaint from customer. The stainless steel get rust problem. Customer performed lab test for the chemical compositions. They sent the rusted part for test. They remove the rust (I don't know whether they totally remove the rust or not). The chemical compositions is as followings. C - 0.063%7E0.079%. Mn - 19.3%7E19.9%. S - 0.011%. P - 0.024%. Si - 0.89 %7E 0.95%. Cr - 8.51 %7E 9.98%. Ni - 0.13 %7E 0.15%. Mo - 0.02 %7E 0.03%. Cu - 0.05 %7E 0.06%. Al - 0.01 %7E 0.025%. Niobium - 0.036 %7E 0.041%. Titanium - 0.018%. Per the result, customer said that material of the part is Manganese steel (NOT stainless steel). However, supplier give us material compositions table as followings. C - 0.08%. Mn - 2.25%. S - 0.024%. P - 0.021%. Si - 0.02%. Cr - 16%. Ni - 6.2 %7E 6.5%. Our questions are as followings. Please advise ASAP. Many thanks. 1) Per our usnderstanding, stainless steel has high Cr and Ni content. Why content of Mn increased per the lab test? Why content of Ni and Cr decreased? Is there any composition change during at the application environment? Does corrosion happen due to decreasing of Ni and Cr? Please advise. Thanks. 2) Does the rust issue happen after one year properly? Can we said corrosion resistance of SUS304 is around one year or shorter under chloride water? 3) Per the material compositions from supplier, can we said that the material is SUS304? (There are variations at Cr and Ni content - 10% each item.) if not, can we said that the material is SUS304 but not good quality? I am looking forwarding to receiving your reseponse ASAP (if possible today). Many many thanks. Regards, Tom.

>Finding lots of Mn in place of Ni is not very uncommon as >it appears. > >Generally speaking, any austenitic SS shall have high %age >of Cr & an 'Austenite stabilizing' element. For any 300 >series variety of aust. SS (like SS 304, SS 316 etc.), the >Aust. stabilizing element is Ni. However, sometimes, >unscrupulous manufacturers use Mn in place of Ni. The Mn >at higher concenration, will stabilize the austenite & you >will get an Aust. SS. However, the corrosion resistance of >these (Mn)aust. SS is likely to be less than any (Ni) aust. >SS. > >In your case the supplier has done the same. We also once >faced same problem when one of dia 8" SS flange cracked in >operation. The supplier had put a cast Mn stabilized aust. >SS in place of forged SS 316 L. > >So, in a nutshell, your chemical analysis results are >correct and you have been duped by the supplier. Next time >you buy a similar piece, at least try to get a chemical test >done beforehand before giving the final payment. > >Regards > >Chakra Dear Chakra, Many thanks for your quick reponse. The supplier is in China. She said that the composition is Chinese SS304 standard. Can you please advise your comment? Can we call the (Mn) asut. SS as SUS304 (at a lower quality margin)? Please advise. As you said, corrosion resistance of these (Mn)aust. SS is likely to be less than any (Ni) aust. >SS. Can you please advise the percentage? We already put the stainless part into swimming pool (has chloride) for one year. We get rust problem one year later. Do you think corrosion resistance of the part is acceptable? Do we need to change material of our part to SUS316? Please advise ASAP. Many thanks. Regards, Tom.