The Role of Oxygen Mass Transfer in the Erosion-Corrosion of Slurry Pipelines

Abstract

The erosion-corrosion of vertical 38-mm diameter pipes carrying aerated slurry (20 vol% – 30 + 50 mesh silica sand) in 3.13% NaCl solution at 2 to 6 m/s has been measured by weight loss measurements over periods of 100 h. Electrochemical methods have been applied to clarify the mechanism of the process and to determine the corrosion component of the metal. Total wear rates in the range of 6 to 25 mm/y were related to the slurry velocity (v) by wearrate=constvn The value of n was in agreement with oxygen mass transfer controlled corrosion being the dominant mode of metal loss, with n ≈ 1. The absolute values of the wear rate were sufficiently close to those measured by electrochemical methods and those calculated from a mass transfer correlation determined for this system, Sh=0.031Re0.83Sc0.33to conclude that the dominant mode of metal loss is corrosion. The role of erosive action in the erosion-corrosion process is to prevent the formation of a complete rust film that normally stifles corrosion and reduces the rate to <1 mm/y, not to yield high erosion rates of the corrosion-roughened surfaces, as previously proposed.