CORROSIVE INFLUENCE OF VARIED SALT SOLUTIONS CONCENTRATION ON MILD STEEL

Abstract

This study is focused on the corrosive effects of varied salt solutions concentration on two mild steel specimens (API 5L X42 and API 5L X60). Gravimetric method was adopted in the evaluation of the weight loss and corrosion rate of the specimens. The hardness of the test specimens after dipping in corrosive solutions was examined. Potentiodynamic polarisation technique was also used to compare the most corrosive medium. API 5L X42 and API 5L X60 specimens exhibited highest corrosion rates of 9.593 mmpy and 9.698 mmpy respectively in solution A that contained 2.0 M NaCl, 3.0 M CaCl2 and 0.5 M Na2CO3. They also exhibited the lowest corrosion rates of 7.642 mmpy and 7.836 mmpy respectively, in solution H that contained 0.5 M NaCl, 3.0 M CaCl2 and 2.5 M Na2CO3. The API 5L X42 mild steel specimen in solution H exhibited the highest hardness value of 369 HV after immersion in the corrosive medium. The hardness of the corroded specimens decreased when compared to their hardness before immersion in the corrosive media, which indicates that the varied salt solutions impaired the surface morphology of the specimens’ thereby promoting indentation.