Zn-Ni-alloy electroplated steels are one of the surface-treated materials with a high corrosion resistance and are mostly used for automobiles. It is said that the corrosion resistance is more than four times as great as that of Zn-plated steels. Concerning x-ray stress measurement, Kyono et al reported the result of measurement on y (552) planes and showed that the sin2φ diagram was severely curved.
X-ray stress analysis in surface-treated materials will become more important. Some problems, however, remain to be studied when we apply the x-ray method to thin layers. For example, the effective x-ray penetration depth may be different from that in ordinary materials. And complex gradients of stresses and compositions may exist.