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首页> 美国政府科技报告 >PROTECTIVE COATINGS FOR MAGNESIUM ALLOYS, PART 2 - RESISTANCE OF FLAME-FUSED TEFLON COATED MAGNESIUM AND ALUMINUM ALLOYS TO CORROSION BY 3% SODIUM CHLORIDE SOLUTIONS
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PROTECTIVE COATINGS FOR MAGNESIUM ALLOYS, PART 2 - RESISTANCE OF FLAME-FUSED TEFLON COATED MAGNESIUM AND ALUMINUM ALLOYS TO CORROSION BY 3% SODIUM CHLORIDE SOLUTIONS

机译：镁合金的防护涂层，第2部分 - 用3％氯化钠溶液腐蚀火焰熔覆的TEFLON涂层镁和铝合金的腐蚀性

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The corrosion resistance toward 3% sodium chloride solution of flame-fused Teflon-coated magnesium alloy AZ31B-H24, and aluminum alloys 2024-T3, 5052-H32, and 6061-T6 has been studied. The formation of pores in the Teflon coatings applied to magnesium alloy AZ31B-H24 is attributed to hydrogen gas which is evolved from the reaction between the highly acidic Teflon formulations and reactive magnesium alloy. Although a methacrylic acid pretreatment of the magnesium test specimens did not reduce pore formation, the presence of a chrome-pickle film on the magnesium alloy specimens and the use of Teflon one-coat green enamel (du Punt 851-204) alleviated pore formation. Cracks which form when the Teflon is flame fused, especially in thick Teflon coatings on aluminum and magnesium alloys, are attributed in part to the volatile tetrafluorethylene formed when the Teflon is thermally degraded during the flame fusion. Mass spectral data indicate that the major decomposition product, tetrafluorethylene, is not altered by the magnesium or glass substrate on which it is present during the thermal decomposition. Teflon one-coat green enamel, which has been applied in thin films, 0.0002 to 0.0004 in. thick, and which has been properly flame fused, will not be wet by the 3% sodium chloride solution during the test period;specimens having such Teflon coatings exhibit enhanced corrosion resistance. Three methods were evaluated as accelerated corrosion tests:an immersion test, a salt droplet test, and a spherical-joint contact test which could be modified to measure the relative resistance of the coated specimens. Magnesium alloy AZ31B-H24, chrome pickled, was most resistant to corrosion when coated with flame-fused Teflon one-coat green enamel;magnesium alloy specimens treated otherwise exhibited enhanced corrosion rates. Aluminum alloy 6061-T6, Teflon coated and flame fused, exhibited the greatest corrosion resistance when compared with the other aluminum alloys tested. No correlation was found between the various aluminum alloy tempers studied and the corrosion rate. In general, the corrosion tests indicate that the flamefused Teflon coating afforded some protection against corrosion as compared to the uncoated specimens.

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