GB/T 11378-1989 "Metal overlay film thickness profile measurement method" is equivalent to ISO 4518:1980, which is a national standard specifying the measurement of metal overlay film thickness and profile size. The content covers measurement principles (such as contact Profile Gauge method), instrument and equipment requirements, sample preparation (surface pretreatment), measurement procedures (scanning speed, sampling length control) and data processing methods. Film thickness and size characteristics are determined by analyzing the surface profile of the overlay. Film thickness testing for metal platings, coatings and other coatings provides a technical basis for evaluating the uniformity and processing accuracy of coatings, and helps to unify measurement methods and improve the accuracy and international comparability of test results.