Accelerated corrosion test involving exposure under controlled conditions of humidity and intermittent spraying of salt solution
Accelerated corrosion tests to simulate atmospheric corrosion in such environments include cyclic exposure to a wet phase, during which the test object is repeatedly subjected first to a spray of salt solution then to a wet stand-by period for several hours. This is followed by a phase of controlled cyclic humidity conditions, where the test object is subjected to an environment which alternates between high humidity and comparative dryness.
In the first (wet) phase of exposure, the test objects are sprayed for 15 min with a 1% (mass fraction) aqueous solution of sodium chloride acidified to pH 4.2, to simulate the rather acidic precipitation present in industrialized areas, followed by a 1 h 45 min period of wet stand-by. This sequence is repeated three times to give a total of 6 h exposure to wetness. The whole of this first phase of the test cycle is repeated twice a week.
The major part of the test cycle, however, consists of humidity cycling between the two levels of 95 % RH and 50 % RH at a constant temperature of 35°C.