Critical Issues for Chrome-free Pretreatment of Aluminium Alloys

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Critical Issues for Chrome-free Pretreatment of Aluminium Alloys Corrosion ranking 10 9 8 7 6 5 4 3 2 1 0 -1 HvH exposure (50/38 months) ASS test (500 h) 3 4 5 6 7 8 9 10 11 12 13 Coil number Comparison of Hoek van Holland Exposure Site Results and ASS test Results for Lightly Cleaned AA3005 Samples (Average values for all coil positions) International Conference on Environmental friendly Pretreatments fo Aluminium and other Metals, Oslo, Norway, June 16-18, 2004
Critical Issues for Chrome-free Pretreatment of Aluminium Alloys Preliminary Analysis of Exposure Site and Corrosion Test Results TNO completed and reported a study of exposure site and corrosion test results on a large set of coil coated steel and aluminium samples. This study included 14 different combinations of pretreatment and coating systems applied to four aluminium alloy substrates (A1: AA3003 H26 max 0.1% Cu, A2: same as A1 but different producer, A3: AA5005 H14 and A4). SystemAlloy Pretreatment Primer Base coat Top coat Remarks S3 A2 NR1 no-rinse chromate P1 epoxy 4-6 µm C1 saturated polyester 17-19 µm S11 A1 NR2 no-rinse chrome/phos B1 polyurethane 16-20 µm C7 PUR/PA transp. 8-12 µm S12 A1 NR4 no-rinse chrome/phos B2 polyurethane met 16-20 µm C7 PUR/PA transp. 8-12 µm S13 A1 NR2 no-rinse chrome/phos P3 acrylate/epoxy 5-7 µm C8 PVDF 80/20. 16-20 µm N4 A1 NR2 no-rinse chrome/phos B4 PVDF 80/20 16-20 µm C15 PVDF 80/20 transp. 8-12 µm N5 A1 NR3 no-rinse chrome/phos B4 PVDF 80/20 16-20 µm C15 PVDF 80/20 transp. 8-12 µm N6 A1 NR3 no-rinse chrome/phos B1 polyurethane 16-20 µm C7 PUR/PA transp. 8-12 µm like S11 N7 A1 NR4 no-rinse chrome/phos B5 polyurethane met/transp. 16-20 C7 µmPUR/PA transp. 8-12 µm N9 A1 NR5 special no-rinse B1 polyurethane 16-20 µm C7 PUR/PA transp. 8-12 µm like S11 N15 A1 NR8 no-rinse grey B6 PVDF 80/20 16-20 µm C16 PVDF 80/20 8-12 µm metallic N17 A4 NR2 no-rinse chrome/phos B1 polyurethane 16-20 µm C7 PUR/PA transp. 8-12 µm like S11 N18 A4 NR4 no-rinse chrome/phos B2 polyurethane met 16-20 µm C7 PUR/PA transp. 8-12 µm like S12 N19 A4 NR2 no-rinse chrome/phos P3 acrylate/epoxy 5-7 µm C8 PVDF 80/20. 16-20 µm like S13 V2 A3 R3 yellow chromate C17 saturated polyester powder 55-110 µm Test panels of most systems and were exposed at three exposure sites for up to 9/10 years (Den Helder, Delft, Hoek van Holland). Panels were also tested using the ABC test, the Prohesion test, with and without QUV, and the TNO cyclic corrosion test with a weatherometer with the Xenon lamp either on or off. Images of the tested panels have been recently made available and the purpose of the present study was to make a detailed analysis of these images to correlate the results of the exposure tests with the corrosion test results on the aluminium substrates. International Conference on Environmental friendly Pretreatments fo Aluminium and other Metals, Oslo, Norway, June 16-18, 2004
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