Kesternich Test

As of this writing the 2inc alloys are too new to have actual corrosion resistance data, except for that based on accelerated tests. Zinc—nickel usually shows better results than 2inc-cobalt in salt spray tests. The reverse is tme when the Kesternich test is used. Tin—2inc performs well in both salt spray and Kesternich tests, but appears only to equal 2inc plating and 2inc—nickel in humidity tests. 

Galvanoaluminum layers thicker than 12 pm are extraordinarily corrosion resistant to exposure to SO2, in which they surpass the performance of cadmium and zinc layers [31]. After 20 rounds of the SFW 2.0 L, DIN 50018 Kesternich test, in contrast to the ca. 12 pm thick, yellow chromated galvanoaluminum layers, the zinc and cadmium coatings were already heavily corroded. The SO2 resistance of anodized galvanoaluminum can also be considered excellent in comparison to cadmium and zinc coatings. 

In the Kesternich test, samples are exposed to water vapor and sulfur dioxide for 8 hours, followed by 16 hours in which the chamber is open to the ambient environment of the laboratory [2]. This test was designed for bare metals exposed to a polluted industrial environment and is fairly good for this purpose. However, the test s relevance for organically coated metals is highly questionable. For the same reason, the similar test ASTM B-605 is not recommended for painted steel. 

Accelerated Corrosion Tests. There are as many as a dozen methods (salt fog, Kesternich, etc.) that are currently being used to investigate corrosion resistance of coating systems and a need to develop a better and more dependable method to predict in-use service. A severe drawback of all these tests is that their results often compare unsatisfactorily with practical experience. One reason for the discrepancies is assumed to be the variability of natural exposure conditions. Accordingly, cyclic testing procedures have been developed with which exposure conditions, especially temperature and humidity. 

Effects of Humid Climates. The specimen is exposed to warm air saturated with water vapor, with or without intermittent cooling to room temperature. The test is very suitable for assessing the corrosion resistance of metals, protective coatings, and composite materials in buildings. For standards, see Table 1 ( Climates Containing evaporated water ). Apparatus Kesternich condensation equipment. 

This approach is useful if the environment is well characterized and a few weeks or months have been allocated for the test examples include exposure to salt spray to simulate sea coastal areas, exposure to 3.5 wt% NaCl solution for submarine environment, Kesternich chamber test (humid SO2 and CO2 mixture) for industrial environment [6], and mixed flowing gas tests for a range of environments. 

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