The apparatus for testing consists of a closed testing cabinet/chamber, where a salt water (5% NaCl) solution is atomized by means of spray nozzle(s) using pressurized air.
Cyclic corrosion testing is better suited to this. The salt spray test has little application in predicting how materials or surface coatings will resist corrosion in the real world, because it does not create, replicate or accelerate real-world corrosive conditions. For this reason, the salt spray test is most often deployed in a quality audit role, where, for example, it can be used to check the effectiveness of a production process, such as the surface coating of a metallic part. Most commonly, the time taken for oxides to appear on the samples under test is compared to expectations, to determine whether the test is passed or failed. The principal application of the salt spray test is, therefore, enabling quick comparisons to be made between actual and expected corrosion resistance. The longer the accelerated corrosion test, the longer the process remains out of control, and larger is the loss in the form of non-conforming batches. Failure to meet this requirement implies instability in the chemical process of the pre-treatment, or the paint quality, which must be addressed immediately so that the upcoming batches are of the desired quality. For example, pre-treated + painted components must pass 96 hours Neutral Salt Spray, to be accepted for production. Most Salt Spray Chambers today are being used NOT to predict the corrosion resistance of a coating, but to maintain coating processes such as pre-treatment and painting, electroplating, galvanizing, and the like, on a comparative basis. Although there may be a weak correlation between the duration in salt spray test and the expected life of a coating in certain coatings such as hot-dip galvanized steel, this test has gained worldwide popularity due to low cost and quick results. Salt spray testing is popular because it is relatively inexpensive, quick, well standardized, and reasonably repeatable.
#MYST SALT ISO#
Other important relevant standards are ISO 9227, JIS Z 2371 and ASTM G85. ASTM B117 was the first internationally recognized salt spray standard, originally published in 1939. The salt spray test is one of the most widespread and long-established corrosion tests. Test duration depends on the corrosion resistance of the coating generally, the more corrosion resistant the coating is, the longer the period of testing before the appearance of corrosion or rust. The appearance of corrosion products ( rust or other oxides) is evaluated after a pre-determined period of time. Salt spray testing is an accelerated corrosion test that produces a corrosive attack to coated samples in order to evaluate (mostly comparatively) the suitability of the coating for use as a protective finish. Usually, the materials to be tested are metallic (although stone, ceramics, and polymers may also be tested) and finished with a surface coating which is intended to provide a degree of corrosion protection to the underlying metal. The salt spray test (or salt fog test) is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings.
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