Accelerated Crevice Corrosion Tests for Stainless Steel in 3% NaCl Solution Containing Activated Carbon

Abstract

Factors involved in the accelerated crevice corrosion test of stainless steel in 3% NaCl solution containing activated carbon have been examined by using a separate anode-cathode system. An anode having a crevice and a cathods were coupled through a zero resistance ammeter and the short circuit current was measured.
The agreement of the weight loss of the anode specimen with the calculated value from the current demostrated that the separate electrode system was useful. The kind of activated carbon affected the corrosion rate, and X7100 gave the maximum value among various kinds. The crevice width was also an important factor and the maximum corrosion rate was observed at the width of 7μm. The location of initial attack and its way of propagation were clarified. The crevice corrosion rate was controlled by the cathodic reaction taking place on the surface of activated carbon. By using the optimized test conditions, stainless steels of different grades were tested, giving a reasonable order of resistance. The effects of the important factors, i. e., the anode/cathode area ratio and the torque with which the crevice was tightened, obtained in the accelerated test were in accordance with those observed in 2 years tests conducted without activated carbon.