A Chemical Test for Identifying the Fraction of Grains in the Surface of Galvanized Steel That Have Orientations Approxi
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IT has recently been shown' that the orientation of the zinc grains is one of the factors that affects the adherence of paint to prepainted galvanized steel during forming operations. Galvanized steel having a high percentage of grains oriented with the (0001) planes parallel to the surface shows the best paint adherence. The degree of (0001) orientation in the previous study was determined by illuminating the surface with a rectangular beam of X-rays while simultaneously rocking the sample through an angle of ±1 deg and rotating it. This method of orientation determination has the shortcomings that a) an X-ray apparatus is required, b) a limited area can be examined at one time, c) the uniformity of the degree of (0001) orientation over large areas is time- consuming to determine, and d) difficulties are experienced in studies of temper rolled (skin passed) material. For these reasons it appeared advisable to develop a chemical technique that was simple and useful in appraising large areas, especially for in-plant quality control. THE CHEMICAL TEST FOR DEGREE OF (0001) ORIENTATION OF ZINC During the preliminary stages of development of the method, three different types of chemical procedures were considered: a) the development of etch pits, b) the development by etching of twin bands formed upon straining, and c) chemical treatments that result in different optical properties on grains of different orientation. The etch pit technique'
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