Monitoring Pitting Corrosion by Holographic Interferometry Available to Purchase

The corrosion current density of aluminum in 5% sulfuric acid (H₂SO₄) and copper in seawater was measured using an optical corrosion meter developed to test and evaluate materials in relation to different corrosion phenomena. The optical corrosion meter is based upon principles of holographic interferometry for measuring microsurface dissolution (i.e., mass loss) and on principles of electrochemistry for measuring bulk electronic current (i.e., corrosion current) of metallic samples in aqueous solutions. In the early stage of corrosion monitoring of both metals, pitting phenomena were observed using holographic interferometry. Observations of pitting basically were interferometric perturbations detected on the surface of both metals. These perturbations were interpreted as localized corrosion in the form of early pitting. Depths ranged between 0.3 μm and several micrometers. Results indicated optical holography is a very useful technique for monitoring pitting at the initiation stage for different metals in aqueous solutions.