A Fresh Look at ASTM G 1-90 Solution Recommended for Cleaning of Corrosion Products Formed on Iron and Steels

ASTM G 1-90 solution, also popularly known as Clarke solution, which contains concentrated hydrochloric acid (HCl, specific gravity [sp.gr.] = 1.19) + 2% antimony trioxide (Sb₂O₃) and 5% stannous chloride (SnCl₂), shows considerable variation in its corrosive effect toward steels having different chemical compositions. Plain carbon steels (PCS) and some low-alloy steels (LAS) experience faster dissolution in comparison to LAS having copper, manganese, silicon, chromium, etc., as alloying elements. The presence of phosphorous in steels has an accelerating effect on corrosion rate. An attempt has been made to bring down the corrosion rate of different types of steels to an equal level by modifying the composition of the ASTM-recommended cleaning solution. Addition of 0.5% copper salt (cuprous chloride [CuCl]) to the Clarke solution has dramatically improved the performance of the solution, and an almost identical rate of corrosion is recorded for all the studied steels. This addition also accelerates the dissolution rate of oxide of steels with variations in their chemical compositions. Electrochemical direct current (DC) polarization and alternating current impedance spectroscopic (EIS) studies have been performed to understand the mechanism of the action of the original and modified solutions in controlling the corrosion of steels.