A chemical treatment applied to ferrous metals to improve their corrosion resistance. The process is based on a manganese phosphate solution that produces a fairly thick coating. This can subsequently be painted or impregnated with oil. A heat treatment process often applied to high carbon wire. The steel is heated to a suitable temperature well above the transformation range, followed by cooling in air or a bath of molten lead or salt. A structure is produced suitable for subsequent cold drawing and which will give the desired mechanical properties in the finished state.