1.Nitric acid point test: a significant feature of stainless steel flange is the inherent corrosion resistance of concentrated nitric acid and dilute nitric acid.This property makes it easily distinguishable from most other metals or alloys.

2.Copper sulfate point test: copper sulfate point test is quickly distinguish ordinary carbon steel and all types of stainless steel the most convenient method.The concentration of copper sulfate solution used is 5~10%.

3.Magnetic test: magnetic test is the difference between annealed austenitic stainless steel and ferritic stainless steel the simplest method.Austenitic stainless steel is non-magnetic steel, but it will be slightly magnetic after cold working under high pressure.And pure chromium steel and low alloy steel are strong magnetic steel.

4.Sulfuric acid test: stainless steel flange test can distinguish 302 and 304 from 316 and 317.The cutting edge of the sample should be finely ground and then cleaned and passivated for half an hour in nitric acid (specific gravity 1.42) with a volume concentration of 20~30% and a temperature of 60~66℃.