EVALUATION OF WATER JET IMPINGEMENT EROSION-CORROSION OF MILD STEEL UNDER EXPERIMENTAL OPERATING CONDITIONS

Abstract

An investigation of waterjet impingement erosion-corrosion of mild steel, a highly corrosion-susceptible but versatile structural material of vast importance, is detailed. The natural downward hose-flow of distilled water containing various concentrations of 0–20% analytical-grade hydrochloric acid (HCl) and 0–20% slurry particles of diameter 0.1–1 mm in an 8-meter-high water tank was nozzle-controlled to impinge surfaces of the steel coupons with flow velocities of 5–25 m/s for 8 hours at 45o and 90o inclination angles. The attendant corrosion of the steel was evaluated by the coupons' weight losses, corrosion penetration rates, and micro-topographical changes. Results indicate that the steel's corrosion rates and weight losses are much higher than values from the pure electrochemical corrosion tests, increase more with the velocity and sand loading than with the acidity level of the water, increase with sand grain sizes, and are greater at 45° than at 90° flow impingement angles. The highest corrosion rates of 6.271 and 5.771 mm/year and weight losses of 124 and 114 mg were obtained at 45o and 90o impingement angles, respectively, with a water concentration of 20% HCl, 20% slurry particles of diameter on mm, and a flow velocity of 25 m/s. Micro-topography analyses of the most corroded coupons by scanning electron microscopy relative to the uncorroded coupons revealed several rough spots, with a greater concentration of them around the center of the coupon surface that was impinged at 90° and random micro-craters of faintly reddish-brown appearances on the coupon that was impinged at 45°.