Corrosion-Resistant Inhibited Coatings for Welded Joints of Pipelines

Abstract

We propose a new polyurethane primer with high adhesion for the protection of welded joints of main pipelines under the field conditions. For the investigation of the influence of filling of this primer by a mixture of modified zinc phosphate and calcite in the form of a finely divided marble powder on its anticorrosion and physicomechanical characteristics, we used contemporary methods of investigations: the electrochemical impedance spectroscopy and scanning electron microscopy. It is shown that the extract of marble powder blocks anodic reactions on the surface of 09G2S pipe steel. Together with zinc phosphate, it forms an efficient corrosion inhibitor of mixed type in weakly acid rain. It is shown that, under the influence of the extract of marble–zinc-phosphate inhibiting composition, the resistance to charge transfer becomes 5–10 times higher depending on the ratio of the modified phosphate to the filler and the time of holding. A stable protective film of complex phosphates forms on the metal surface. The procedure of filing of the polyurethane primer with the indicated mixture of inhibitors is promising in guaranteeing the stability of its adhesion in sections of welded joints and metal structures of the main pipelines.