Exposure Conditions for Cyclic Corrosion Testing
October 28, 2020
■Room temperature conditions:
In the cyclic corrosion salt spray test, the room temperature environment refers to the laboratory room temperature conditions. Room temperature conditions can usually change the performance of the test sample very slowly. For example, the sample after the salt spray spray is placed at room temperature for two hours. The sample actually undergoes a slow drying process under certain temperature and humidity conditions. The temperature is 25±5℃ and the relative humidity is 50% or lower.
■Salt mist (spray) conditions:
The salt spray conditions can be achieved in a B117 type test box, or manually operated under laboratory conditions. The nozzle can spray a mist of salt solution. Generally speaking, in addition to NaCl (sodium chloride), electrolytes containing other chemicals can also be used to simulate acid rain or other industrial corrosion.
Cyclic corrosion salt spray test procedures usually require high humidity conditions. The relative humidity requirement is 95-100%. The ASTM D224711 test standard has this requirement. Sometimes it can also be achieved by spraying pure water mist with B117 test box.
Drying conditions can be achieved in an open laboratory or in a test chamber. There is sufficient air circulation in the space to avoid stratification and dry the sample. The definition of "dry" is more complicated, and people still have disputes about whether the surface of the sample is dry or completely dry. As product corrosion penetrates, the time required for the sample to completely dry may increase.
■Water immersion conditions:
Must use distilled or deionized water. For water quality requirements, please refer to ASTM D119312. The soaking container should be made of plastic or other inert materials. The pH of the soaking solution is between 6 and 8, the temperature is 24±3℃, and the conductivity should be less than 50 mo hm/cm at 25 ℃.