Correct selection of stainless steel

Atmospheric environment

Generally, Cr13, Cr17, or 304 stainless steel materials are selected.

Water

304, 316 and other stainless steel materials can resist chloride corrosion.

Molybdenum stainless steel with high chromium and nickel or duplex stainless steel shall be used in seawater.

Nitric acid

In dilute nitric acid (≤ 65%), 304 stainless steel can be selected, because it has good nitric acid corrosion resistance.

With the increase of the concentration, 310 heat-resistant stainless steel can be selected when the concentration is above 68.4%.

When the concentration rises to ≥ 85%, high chromium austenitic stainless steel containing silicon will be used.

Sulphuric acid

The stainless steel without molybdenum cannot be used for sulfuric acid corrosion resistance, while the 316 series stainless steel with 2-3% molybdenum is the lowest grade for sulfuric acid corrosion resistance, and the duplex steel with molybdenum is also equivalent to or better than the 316 series stainless steel.

With the increase of sulfuric acid concentration, it is necessary to select austenitic stainless steel with high chromium and nickel, copper and silicon.

Hydrochloric acid

The medium of hydrochloric acid has strong reducibility, and stainless steel is difficult to be passivated. Austenitic stainless steel with high chromium, high nickel, copper and silicon should be used in dilute hydrochloric acid.

Alkali

Pure ferritic stainless steel containing chromium (≥ 26%) or chromium nickel austenitic stainless steel containing nickel (≥ 20%) shall be selected.

Organic acid

Generally, Cr17 stainless steel or austenitic stainless steel containing molybdenum can be selected.

Prevent local corrosion

Intercrystalline corrosion: 321 stainless steel, 304L stainless steel, 316Ti stainless steel, 347 stainless steel and other materials can be selected.

Spot corrosion: austenitic stainless steel 316L containing molybdenum, high purity ferritic stainless steel SUS444, duplex stainless steel 18-5, 2205, etc. can be selected.

Crevice corrosion: Generally, the stainless steel with resistance to spot corrosion can be selected.

Stress corrosion: 316 series stainless steel and duplex stainless steel can be selected.