Abstract: Corrosion performance of 20 steel was improved by low temperature gas multi-element penetration technique.Carbon,nitrogen and oxygen were infiltrated into the material.The phase constituents of the alloying layer were investigated by XRD.The corrosion resistance of the penetrated layer and original material was compared by electrochemical method in 1.0 mol/L HCl solution.The results show that the penetrated layer consists of oxide,nitride and carbide.Among them the nitride is predominant.In comparison with the original material,the penetrated layer has much better corrosion resistance and lower corrosion rate.