Galvanic Corrosion of the Base AISI 316l/Micro-Plasma Arc Welded AISI 316l in Polluted Phosphoric Acid Media at Different Temperatures

In this work, the galvanic corrosion of the base AISI 316L stainless steel/micro-plasma arc welded AISI 316L stainless steel in phosphoric acid solutions polluted with sulphuric acid and chlorides was studied by means of the Zero-Resistance Ammeter technique. Experiments were performed at different temperatures (25, 40 and 60 degrees C) under flowing conditions (Reynolds number of 1456). Galvanic current density values are negative during the first hour of the test indicating that the welded alloy is corroding; then, they shift towards positive values indicating that the base stainless steel corrodes. Galvanic current density values reached stable values from the third hour of the tests performed at 25 and 40 degrees C, and during the last two hours of the test at 60 degrees C indicating passivation of the base alloy. Uniform corrosion processes occur for the AISI 316L alloy in polluted phosphoric acid solutions. Galvanic current densities increase with temperature according to Arrhenius plot. Impurities seem to increase galvanic corrosion and hinder passivation processes.