The standard is ISO 3231-1993 "Determination of moisture resistance of Paints and varnishes containing sulfur dioxide". The standard specifies the method for testing the corrosion resistance performance of Paints and varnishes coatings through a humid environment containing sulfur dioxide, covering the test principle, equipment construction, gas concentration control, exposure process and result evaluation. By simulating the synergistic effect of sulfur dioxide and moisture in an industrial polluted environment, the tolerance of coatings under acidic corrosion conditions can be evaluated, providing technical specifications for chemical corrosion performance testing of Coatings and industrial protection applications.