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Corrosion Control Through Organic Coatings Part 10

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Tham khảo tài liệu 'corrosion control through organic coatings part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 132 Corrosion Control Through Organic Coatings most automotive tests including the cyclic corrosion tests have been developed using coatings relevant to automotive application. These are designed to act quite different from protective coatings. Automotive-derived test methods commonly overlook factors critical to protective coatings such as weathering and UV factors. In addition automotive coatings have much lower dry film thickness than do many protective coatings this is important for mass-transport phenomena. This section is not intended as an overview of automotive industry tests. Some tests that have good correlation to actual field service for cars and trucks such as the Ford APGE Nissan CCT-IV and GM 9540P 4 are not described here. The three tests described here are those believed to be adaptable to heavy maintenance coatings VDA 621-415 the Volvo Indoor Corrosion Test VICT and the Society of Automotive Engineers SAE J2334. 8.1.4.1 VDA 621-415 For many years the automotive industry in Germany has used an accelerated test method for organic coatings called the VDA 621-415 5 this test has begun to be used as a test for heavy infrastructure paints also. The test consists of 6 to 12 cycles of neutral salt spray as per DIN 50021 and 4 cycles in an alternating condensation water climate as per DIN 50017 . The time-of-wetness of the test is very high which implies poor correlation to actual service for zinc pigments or galvanized steel. It is expected that zinc will undergo a completely different corrosion mechanism in the nearly constant wetness of the test than the mechanism that takes place in actual field service. The ability of the test to predict the actual performance of zinc-coated substrates and zinc-containing paints must be carefully examined because these materials are commonly used in the corrosion engineering field. Also the start of the test 24 hours of 40 C salt spray has been criticized as unrealistically harsh for latex coatings. 8.1.4.2 Volvo .