Among the test methods of the salt spray test chamber, the intermittent spray test method can be used as an alternative to the continuous spray test method. This test result has a better correlation with the exposure test results in environments where chloride ions have an important influence (salt comes from seawater or roads with antifreeze salt applied).
In this case, accelerated corrosion that simulates atmospheric corrosion should include the process of cyclic exposure to the following environments:
a) Wet stage, at this stage the sample is first exposed to salt spray conditions, followed by the moisturizing period, and so on. During the moisturizing period, the surface of the sample remains moist. The above process provides continuous exposure to a wet state for up to several hours;
b) In the stage of controlling circulating humidity, the sample is usually placed in an alternating environment of relatively high humidity and low humidity.
These two phases should be cycled the appropriate number of times:
In the first wet exposure stage, adjust the pH of the 1% (mass fraction) NaC1 aqueous solution to 4.2 with acid and spray it onto the surface of the measured object for 15 minutes to simulate the acid settlement existing in the industrial zone; then the moisturizing period of 1h45min . Repeat the above process three times to make the exposure in a wet state for 6h. The entire process of the first phase of the test cycle is repeated twice a week. If the spraying is delayed too frequently, or the concentration of the sodium chloride solution used at this stage is too high, there will be some phenomena that rarely occur outdoors.
The main part of the test cycle consists of the humidity cycle, that is, at a constant temperature of 35 ° C, alternating between 95% RH and 50% RH. In order to simulate the wet state of the humidity cycle of the salt spray test chamber, it will inevitably lead to an uncontrollable amount of salt deposited on the measured object.
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