Particle velocity effects on erosion-corrosion of AISI 1020 carbon steel in CO2-saturated drilling mud

Abstract

A systematic approach was adopted to independently assess erosion, corrosion, and their combined effects under controlled flow conditions that closely mimic real drilling environ-ments. This study offers in-depth insight into how increasing flow velocities alter the preva-iling degradation mechanism, transitioning from corrosion-dominated behaviour at lower speeds to erosion-driven processes at higher speeds. The effect of particle velocity on the erosion-corrosion behaviour of AISI 1020 carbon steel was investigated in a CO₂-saturated, water-based drilling mud containing 3.5 wt.% NaCl and 500 mg L-1 of sand particles (400 to 500 μm in size). Experiments were conducted using a custom jet impingement flow loop at velocities ranging from 5 to 20 m s-1. Degradation rates and surface deterioration were evaluated through total weight loss measurements and detailed analysis using scanning electron microscopy. The results demonstrate a substantial increase in material loss as flow velocity rises, with degradation rates exceeding 20 mm year-1 at 20 m s-1. The synergistic interaction between erosion and corrosion was most evident at lower velocities, whereas erosion alone became predominant at higher velocities. Independent erosion and corrosion tests confirmed that the material loss was caused by the combined influence of mechanical impact and electrochemical reactions. These findings emphasize that synergy decreases with increasing velocity, highlighting the transition from corrosion-assisted erosion to erosion-dominated degradation. The results provide critical insight into the velocity-dependent mechanisms of erosion–corrosion and reinforce the need for velocity management strategies to extend the service life of steel components in drilling operations.