Abstract
A series of AlN thin films was synthesized on Al-25mass%Mg substrate under different Ar pressures from 007 to 1.3Pa using rf magnetron sputtering. The effects of Ar pressure on the corrosion protection in a 5mass%NaCl solution and structural properties were studied. As Ar pressure was increased above 027Pa, the corrosion resistance of the AlN-coated Al-Mg alloy was significantly improved. Residual film stress was compressive under low Ar pressures, which decreased as Ar pressure increased and turned tensile at high Ar pressures. An obvious correlation was observed between the corrosion protection property and residual stress. A coating with low residual stress was superior in corrosion protection to a coating with high compressive residual stress. The change of the corrosion protection property is discussed in connection with the residual stress of the sputtered film. The origin of the residual stress in the AlN coating is also discussed from the viewpoint of the energy change in sputtered particles.
