GB/T 30789.3-2014 "Paints and varnishes – Evaluation of degradation of coatings – Designation of quantity and size of defects, and of intensity of uniform changes in appearance – Part 3: Assessment of degree of rusting" is part of a series of standards for evaluating coating aging. It specifies the method for assessing the degree of rusting after coating aging. The assessment is primarily based on the proportion of rusted area and the severity of corrosion. By referencing standard rating charts, ensuring consistent observation conditions with a standard light box, and using a magnifying glass to assist in identifying fine corrosion, this standard provides a standardized basis for evaluating the anti-corrosion performance of coatings, ensuring the objectivity and comparability of assessment results.