Effect of Residual Stress-Strain Profile on Hydrogen Embrittlement Susceptibility of Prestressing Steel Wires

Cold drawn wires of eutectoid pearlitic steel are widely used for prestressing concrete structures which usually work in hostile or aggressive environments, so that stress corrosion cracking of prestressing steel is a problem of major technological concern. In addition, there is general agreement that hydrogen embrittlement (HE) plays an important role in the environmental cracking of such a steel due to particular working conditions or to the local electrochemistry in the vicinity of a crack tip. In this framework, the Standard Test in Ammonium Thiocyanate was proposed by the International Federation of Prestressing (FIP) as a suitable experimental method for checking the susceptibility of high-strength prestressing steels to stress corrosion cracking in general, and particularly to hydrogen embrittlement. In spite of some objections to this standard corrosion test, it is the best suited for steel control and acceptance. However, the main disadvantage of the FIP test is the scattering of the results, which increases as the externally applied stress decreases. It can be caused by the distribution of residual stresses generated in the vicinity of the wire surface during the manufacturing (cold drawing) process.