Corrosion resistance improvement of nitrocarburised and post-oxidised steels by oil impregnation

Nitrocarburising is a well known process developed to improve superficial hardness and wear resistance of steels; a subsequent post-oxidation step is often useful to enhance the corrosion resistance. In this work, an additional step was evaluated: nitrocarburised and post-oxidised parts were impregnated in lubricant oil in order to improve their wear and corrosion resistance. The effectiveness of this new treatment, in terms of corrosion resistance, was assessed for two steels, 20MnCr5 and 42CrMo4, using two different oils. The results obtained from corrosion tests show that the impregnation treatment increases the corrosion resistance, in both acidic and chlorurated media.