Transgranular Stress Corrosion Cracking of Mild Steel in 0.5N H₂SO₄ + 0.005N KI Solution — XPS Observation of the Surface Film Available to Purchase

The surface film formed on strained mild steel in 0.5N H₂SO₄ containing 0.005N KI was examined by XPS in connection with the SCO susceptibility which is highest around 0.06 V relative to the corrosion potential. The film was found to consist mainly of FeOOH containing small amounts of sulfur and iodide. The iodide content alone varied with the polarization potential and had a critical potential coinciding with that for the SCC susceptibility, which is explained by the instability of the surface film at the potential.