A preparation technique for the production of cross-sectional transmission electron microscope (TEM) samples from the interdiffusion regions of Fe-Zn binary couples is described. To alleviate the problem of unequal ion milling rates between the Fe and Zn, a 0.75mm thick Fe sheet has been double plated with a thick electrodeposited Zn coating to achieve a total couple thickness of ˜3mm. After slicing the couple in cross-section, the Fe region of the sample is dimpled to perforation near the Fe-Zn interface. Final thinning for TEM analysis is obtained by ion milling using a liquid nitrogen cold stage and sector speed control. The ion milling procedure is stopped when the perforated hole in the Fe-side of the couple extends through the faster eroding Zn-side of the interface. This technique, in modified form, is expected to be suitable for commercial steels coated with Zn-based alloys.