1, nitric point test of stainless steel pipe tube A striking feature is the concentrated nitric acid and dilute nitric acid with inherent corrosion resistance. This performance so that it can be easily removed from most of the other metal or alloy distinction. However, high carbon steel type 420 and 440 points during nitrate test is slightly affected by corrosion, non-ferrous metals encountered in concentrated nitric acid as soon as may be corroded. And dilute nitric acid on carbon steel has a strong corrosive
2, magnetic test test to distinguish between magnetic annealing austenitic stainless steel and ferritic stainless steel pipe the easiest way. Non-magnetic austenitic stainless steel pipe, but after large cold will have a slightly depressed magnetic; and pure chromium steel and low alloy steel are strong magnetic steel.
3, sulfuric acid immersion test test stainless steel pipe can 302 and 304 and 316 and 317 separate. Trimming the sample should be subject to fine grinding, and then the volume concentration of 20 ~ 30%, temperature 60 ~ 66 �� of nitric acid (specific gravity 1.42) in the cleaning and passivation half an hour. Volume of sulfuric acid test solution concentration of 10%, heated to 71 �� when the .302 and 304 steel when immersed in this hot solution was rapid corrosion and produce a large number of bubbles, the specimen in the dark within a few minutes; while 316 and 317 steel specimens are not subject to corrosion or reaction is very slow (no bubbles), the specimen in the 10 to 15 minutes does not change color. At the same time if we adopt the test sample with a known composition to carry out approximate comparison, can test more accurate.
4, copper sulfate copper sulfate test point test point is a fast distinction between ordinary carbon steel and all types of stainless steel pipe the most convenient way. Copper sulfate solution used in the concentration of 5 ~ 10%. Point test before conducting the test area should be thoroughly remove grease or a variety of impurities, and used Polishing cloth polishing a small area and then it drops after the bottle to the clean-up of regional infusion of copper sulfate solution. Ordinary carbon steel or iron in the formation of a layer within a few seconds, the surface of metallic copper, and stainless steel pipe is not produced on the surface of copper precipitate or show the color of copper.