Experimental study on under-deposit corrosion and its inhibition using electrochemical methods and electronic coupon technique

Purpose In this study the aim was to investigate under-deposit corrosion (UDC) behavior and the action effects of amino trimethylene phosphonic acid (ATMP) in the oxygen-contained solution. Design/methodology/approach Electrochemical methods and wire beam electrode techniques were used for the study of ATMP action effect for X65 steel under silica sand and CaCO3 particle deposit. Electronic coupon technique was used for the study of galvanic effect caused by the deposits and the action effect of ATMP. Findings ATMP would cause localized corrosion for the silica sand-covered steel. However, it could inhibit the localized corrosion of the steel beneath CaCO3 particle deposit. Galvanic effect test showed that the galvanic effect caused by the deposits was an important factor for the acceleration of UDC. ATMP had an obvious promotion effect for the galvanic current between bare coupon and silica sand covered coupon and different degrees of localized corrosion were observed beneath both deposits. Originality/value The authors believe that the paper may be of particular interest to the readers of the journal as the measurement methods for the UDC of X65 pipeline steel. The experiment they did in the laboratory found that the inhibitor ATMP has a good inhibition effect for bare steel, but it would accelerate the UDC. Different kinds of deposits would have different influences for the UDC behavior with inhibitor added.