Sucker Rod Materials - Metallurgical Quality Evaluation and Its Influence on General Corrosion Resistance

摘要

Sucker rod pumps are widely used in artificial lift technology of Oil & Gas production. Corrosion, fatigue and corrosion-fatigue are common failure modes that limit life of the sucker rods that drive these pumps. Of these, corrosion fatigue is probably the most common. The initiation site for corrosion fatigue is typically a corrosion pit. The factors that contribute to the formation of corrosion pits were investigated. Four different sucker rod materials were evaluated with respect to (1) chemistry, (2) non-metallic inclusion content and (3) microstructural investigation including banding severity. It was concluded that microstructural banding has a negative influence on the general corrosion rates. The higher values of quantitively measured banding lead to increased general corrosion rates. The electrochemical potential differences between the light and dark bands is proposed as the cause of locally accelerated corrosion resulting in pits. The dark bands in the less corrosion resistant samples were lower bainite and these were presented as being more anodic.