Cracking of Ti-6Al-4V in Methanol Solutions Containing Sulfates

Whether cracking of unnothched Ti-6Al-4V specimens occurs in methanol solutions containing H₂SO₄, Li₂SO₄, or Fe₂(SO₄)₃ is a function of the age of the solution and the concentration of the sulfate. With H₂SO₄ concentrations of 0.10 N to 0.25 N the methanol solutions lose their ability to crack the specimens with time after mixing and prior to exposure. The aging time required to inhibit the cracking varies inversely with the water content of the solution. With larger quantities of H₂SO₄, 0.5 N and 1 N, no cracking is observed. Interpretations of Raman spectroscopic studies of the aging solution suggests that the nature of the O-H group may play a role in the crack initiation or inhibiting mechanism.