FTIR Measurements of Iron Oxides on Low Alloy Steel

Well‐resolved FTIR spectra of iron oxide and iron carbonate corrosion scales are readily measurable with commercial instrumentation on otherwise untreated low alloy steel coupons. These spectra are relatable to the chemical history of the corrosion process. The absorption maxima of most of the 11 crystalline iron oxides and iron carbonate are sufficiently separated from one another to allow "fingerprinting" many of the films/scales. Exposing some of these films to vacuum drastically alters the position of the absorption maxima. Forming such scales into pellets can also alter the absorption maxima, depending on the particular oxide composition.