Accelerated corrosion tests of precoated sheet steels for automobiles

Abstract

Precoated steel sheet is utilized extensively by the automobile industry in the production of vehicles with increased protection against corrosion. Laboratory accelerated corrosion tests such as the satt-spray test and the cyclic tests, which involve atternating cycles of saltwater immersion and humidity-chamber exposure, are widely used to make preliminary evaluations of the various precoated products. This paper reports the results of salt-spray and cyclic tests conducted on a variety of precoated sheet products. The precoated sheets were tested both with and without additional applicatlon of cathodically deposited electrophoretic primer. Results are compared to those for ordinary sheet steel coated only with primer and are discussed in terms of the degree of protection provided by barrier and galvanic mechanisms, as determined in separate electrochemical measurements. dale, PA, 1980; SAE 800443. VandeWalle, L. J., Ed. "Efflcient Materlals and Coating Appiicatlons for Improved Design and Corrosion Resistance"; American Society for Metals: Metals Park, OH, 1981. Wiggle, R. R.; Smith, A. G.; Petroveiii, J. V. J .

Corrosion Performance of Buried Corrugated Galvanized Steel under Accelerated Wetting/Drying Cyclic Corrosion Test

“…It has been noted that as the temperature increases the resistance against corrosion of the galvanized steel reduces, indicating higher corrosion rates [37]. For example, Cox [38] investigated the temperature impact on the developed corrosion rates of zinc in distilled water up to 100 • C. The results of the zinc corrosion rate showed a very small increase as the temperature increased up to 50 • C followed by a rapid increase at approximately 65 • C, above which the corrosion rate decreased rapidly until reaching 100 • C to have a low corrosion rate almost similar to the corrosion rate at 50 • C. Hence, several cyclic accelerated corrosion tests available in the literature were performed on zinc-coated steel (e.g., galvanized steel) with temperatures of up to 60 • C in the dry stage, e.g., the accelerated corrosion test, method B in General Motors Engineering Standard [39], the accelerated corrosion test for electrical appliances (ACTE) [40], and other research regarding cyclic corrosion tests [25,41]. In the present study, the cyclic accelerated corrosion test on the galvanized coupons was performed under the same test conditions through which mild steel coupons were tested to compare and assess the two states, the mild steel (i.e., low corrosion resistance) and the galvanized steel (i.e., high corrosion resistance).…”

“…Several researchers have performed cyclic accelerated corrosion tests on uncoated and coated (e.g., zinc-coated) metal specimens to accelerate the propagation of rust layers and monitor the corrosion process [21][22][23]. Many of these tests have focused on detecting atmospheric corrosion of open-air coupons (e.g., hot dip galvanized perforation coupons) to study the impact of important climate parameters such as temperature, drying level, relative humidity, duration of humidity cycles, intensity (i.e., concentration) of sodium chloride (NaCl, %), and frequency of exposure to salt spray solutions [24,25]. Furthermore, some accelerated tests have been used to provide preliminary evaluations of various precoated products to examine the degree of protection provided [25,26].…”

“…Many of these tests have focused on detecting atmospheric corrosion of open-air coupons (e.g., hot dip galvanized perforation coupons) to study the impact of important climate parameters such as temperature, drying level, relative humidity, duration of humidity cycles, intensity (i.e., concentration) of sodium chloride (NaCl, %), and frequency of exposure to salt spray solutions [24,25]. Furthermore, some accelerated tests have been used to provide preliminary evaluations of various precoated products to examine the degree of protection provided [25,26]. Other research has been performed to calibrate accelerated cyclic corrosion tests, introduced in wellknown standards, and compared to field exposure tests, to supply correlations based on acceleration coefficients for the laboratory tests [27].…”

Mechanisms of Cosmetic Corrosion in Painted Zinc and Zinc-Alloy-Coated Sheet Steels

“…The laffer aspect, namely, the mechanism of cosmetic corrosion on painted steel, zinc, and zinc alloy coatings, has been the focus of numerous recent investigations. [1][2][3][4][5] A brief summary of conclusions from these studies, given below, serves to illustrate the complexity of the cosmetic corrosion problem.…”