EFFICIENCY OF PROTECTION METHODS AGAINST CORROSION-FATIGUE DAMAGE OF D16T ALUMINUM ALLOY

The results of corrosion-fatigue studies on the D16T aluminum alloy after its protection by different methods are presented. The effects of cathodic polarization, surface-plastic deformation, zinc and nickel electroplating, and corrosion inhibitor on its fatigue and corrosion-fatigue characteristics are investigated. It is established that shot blasting and rolling (surface treatment by rollers) increase the fatigue limit of duralumin in the air almost equally and by similar to 20 and similar to 50% in a 3% NaCl solution, respectively. Such difference in the material's fatigue limits in chlorine-containing medium is due to the higher electrochemical heterogeneity and roughness of the surface after blasting and the different nature of its dissolution. The maximum increase in corrosion endurance of the alloy under cathodic polarization is observed beyond the electrode potential of -1200 mV. At the same time, an increase in the corrosion-fatigue limit by similar to 50% compared to the unprotected material was recorded. To improve the fatigue characteristics of the alloy in the air and chloride-containing environment with zinc or nickel electroplating, it is necessary to carry out preliminary surface-plastic deformation of the material. The porous nickel coating significantly increased the corrosion resistance of the unloaded alloy in a 3% solution of NaCl but reduced the fatigue limit in the air and chlorine-containing medium by similar to 2.5 times, due to generated tensile stresses. Zinc coating significantly reduced the dissolution rate of duralumin in a 3% NaCl solution. In addition, it is established that the coating on the ground surface of the alloy insignificantly lowers the fatigue limit, but increases it by 25-30% in the corrosive environment due to its protective action. The strontium chromate effect on the corrosion-fatigue strength of D16T alloy was studied, and its addition in the amount of 0.6 g/L significantly increased the resistance to corrosion-fatigue failure of duralumin alloy in synthetic acid rain.