This standard specifies a natural environmental test method for evaluating the corrosion resistance of materials and products under outdoor rain conditions. The method involves periodic artificial spraying of test specimens using specific devices to simulate and accelerate the corrosion effects of actual precipitation processes. It is applicable to materials such as metals and their alloys, metallic coatings, anodized films, and conversion coatings. The standard covers test principles, equipment requirements (such as the spraying system), test conditions, specific operating procedures, data recording and processing, as well as the preparation of the final test report. This method provides important technical support for the weathering resistance assessment of products in industries such as metallurgy, automotive, shipbuilding, and aerospace.