The Kesternich test is a common name for the corrosion test with sulfur dioxide (SO) under general moisture condensation. This test was developed in 1951 by Wilhelm Kesternich to simulate the damaging effects of acid rain. 
Acid rain and acidic industrial pollutants are corrosive and can degrade coatings and plated surfaces. Kesternich testing, or sulfur dioxide testing, simulates acid rain or industrial chemical exposure to evaluate the relative corrosion resistance of the coating, substrate, or part itself. The test can be used for coatings or for base materials. 
The test method is defined by various standards,  DIN EN ISO 6988, DIN 50018, ASTM G87, ISO 3231, ISO 22479 are the most common. The parts to be tested are placed in a test chamber with a capacity of 300L and exposed to warm, moist air in combination with a certain amount of sulfur dioxide
Note: Sulfur is interchangeable with Sulphur and SO2 is the abbreviation for Sulfur/Sulphur Dioxide