Technological method of environment-friendly passivation system for pretreatment of aluminum alloy spraying profile

Abstract

The invention discloses a process method of an environment-friendly passivation system for pretreatment of an aluminum alloy spraying profile, which comprises three-in-one phosphorus-free alkaline degreasing, the three-in-one phosphorus-free alkaline degreasing adopts a phosphorus-free, ammonia-nitrogen-free and fluorine-free formula to ensure that a medicament is environment-friendly, and a fluorine-free and zirconium-free passivation technology capable of forming a conversion film on aluminum alloy hydrated alumina is adopted. A natural oxide film does not need to be completely removed, a weakly alkaline buffer system with relatively weak corrosion capability can be adopted, the alkaline degreasing working solution is a weakly alkaline buffer system with the pH value of 9.5-10.5, and a fluoride-free zirconium-free passivation formula in the system avoids dependence of generation of a conversion film on removal of the natural oxide film for degreasing; a technical basis is provided for selecting weakly-alkaline degreasing with weak corrosion capacity, and a process scheme matched with the normal-temperature phosphorus-free weakly-alkaline three-in-one degreasing agent is realized.

Description

technical field [0001] The invention relates to the technical field of chemical industry, in particular to a process method for the pretreatment of an environment-friendly passivation system for aluminum alloy sprayed profiles. Background technique [0002] In recent years, the proportion of spray-treated profiles in aluminum alloy surface-treated profiles has increased year by year. In 2019, the total amount of surface-treated aluminum alloy extruded profiles in China was 14.95 million tons, of which anodic oxidation and electrophoresis accounted for only 20.0% (2.99 million tons) respectively. and 7.5% (1.121 million tons), while the proportion of aluminum alloy sprayed profiles has risen to as high as 72.5%, of which fluorocarbon spray paint accounts for 3.6% (538,000 tons), while powder sprayed profiles with environmental protection advantages are as high as 68.9% (10.301 million tons) ), the aluminum alloy must be treated with a conversion coating before spraying, the e...

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Problems solved by technology

As a result, the degreasing bath requires high concentration, the amount of aluminum dissolved in the degreasing treatment rises rapidly, the aging of the bath is rapid, and the bath is replaced frequently, resulting in high pressure for wastewater treatment; alkali degreasing requires a high concentration, which is different from acidic chromium-free passivation The matching is difficult and the etching speed is high, resulting in the existence of uneven corrosion spots, uneven appearance after painting, and obvious alkali etching dust on the surface after degreasing. It is necessary to increase the neutralization process to remove the surface dust. Correspondingly, two water washing processes need to be added, and large-scale investment and transformation of the current acid degreasing production line is required. If degreasing with strong alkalinity is used, acid neutralization and neutralization water washing are not added, and then alkaline washing is carried out. Obvious and with hanging ash, the pollution to the current acidic chromium-free passivation is faster, and the life of the passivation tank is greatly shortened; the quality of the film is highly sensitive to concentration and time, and the upper limit of the current chromium-free passivation time is generally 2 minutes. Narrow, which is not conducive to on-site control, and there is a potential quality risk. If the conversion film is too thick, decoating will occur. If it is passivated for a long time, it cannot be found and treated effectively, which will cause extremely serious batch quality accidents; the corrosion resistance is not enough. It has fully reached the level of chromate passivation treatment. The pass rate of AASS test is generally low for 1000 hours in the test items. The storage quality risk of the no-water washing process after passivation: A. The effusion level is too passivated. B. The pH value is 2.8- 3.8 Acidic passivation solution and fluoride ions adhere to the surface

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