The theory of metallic corrosion in the light of quantitative measurements. Part V. —The corrosion of iron and mild steel

The measurement of corrosion by the oxygen-absorption method developed for zinc has now been applied to iron. Since the corrosion products contain mixtures of ferrous and ferric compounds, analyses must be made at the end of various corrosion periods to determine the proportions of oxygen used in corrosion and in the secondary oxidation to the higher valency. Notwith­ standing this additional operation, the corrosion measurements have nearly the same order of reproducibility as those for zinc except in special conditions which will be noted later. Three materials have been used, namely :— (1) Highly purified iron prepared by electro-deposition and subsequently meltingin vacuo in a high frequency furnace. (2) Mild steel made in the usual way for tube manufacture, but specially examined for homogeneity. (3) An ordinary sample of mild steel rod taken from a workshop store.