The effect of soft tap water chemistry on fatigue crack growth of steel

Abstract

The electrochemical effects of water chemistry on fatigue crack growth of AISI 1018 steel are investigated. Results obtained show that by changing the langelier index from typical negative values of soft tap waters to positive values by adding appropriate amounts of sodium bicarbonate, the fatigue crack growth rate is reduced, thus resulting in a longer life for a structure subjected to this environment. An attempt is made to explain this phenomenon and to supplement mechanical testing using electrochemical corrosion measurements. Electrochemical corrosion measurements were conducted using cyclic potentiodynamic scans in order to elucidate localized corrosion activity and Small Amplitude Cyclic Voltammetry (SACV) to investigate uniform corrosion activity. Results agree with previous findings, in that as long as the Langelier index is greater than 0.3, both uniform and localized corrosion tendencies are reduced.