Fractographic observations on chloride stress corrosion cracking of type 304 stainless steel under salt crust

The chloride stress corrosion cracking occurring under salt crust formed on heated Type 304 austenitic stainless steels was investigated using fractographic examination by scanning electron microscopy and optical microscopy. Slow strain rate tests were carried out under wick test conditions. Tests have been conducted at 100 °C specimen temperature, 1.9 x 10 -5 mm s -1 crosshead speed and 130°C specimen temperature, 1.38 x 10 -5 mm s -1 crosshead speed. The tests showed that the stress corrosion cracks occurred under the salt crust formed by evaporation of dilute chloride solution containing 1500 ppm chloride ions. The initiation, propagation and density of cracks depend on specimen temperature and crosshead speed.