The Effect of Stray Direct Current at Various Current Densities on the Corrosion of Steel.

摘要

Serious corrosion attributable to stray current has occurred in seawater or brackish water on several occasions where the possibility of the corrosion being from improper welding was precluded. The experimental technique used isolates the bipolar anodes and bipolar cathodes so that stray current corrosion parameters can be studied and quantized. Data are presented on the effect of various stray dc densities on the corrosion rates and the electrode potentials of steel both as common electrodes and as bipolar (or intermediate) electrodes. The metal-loss rates have also been compared to the theoretical values based on the reaction Fe-2e=Fe(2+). The mean dissolution potential for steel in 0.6M (3.5%) NaCl solution was approximately -0.7 V to the Ag/AgCl reference electrode,and was essentially independent of the current density. Similar values were observed for anodes,bipolar anodes and freely corroding control specimens. Potential measurement can be used to detect stray current on steel only at relatively high current densities. The corrosion characteristics of steel anodes and bipolar anodes were similar at any one current density,but varied with current density. (Modified author abstract)