Chromium-free coating agent and preparation method thereof

Abstract

The invention relates to the field of a metal surface treatment agent, and particularly relates to a chromium-free coating agent and a preparation method thereof. The chromium-free coating agent is prepared from the following raw materials by mass percent: 2-6% of hexafluorozirconic acid, 1.7-6.7% of composite silane coupling agent, 0.8-1.5% of zirconium oxychloride, 0.5-1% of citric acid and the balance of water. The chromium-free coating agent does not contain chromium ions, has the characteristics of being short in treatment time, less in sediments, compact in crystal, stable in bath solution, easy to manage and the like, and is especially applicable to surface treatment of aluminum and aluminum alloy before coating. A layer of colorless corrosion-resistant passivation layer can be formed on the aluminum surface in a spraying or soaking manner, so that the adhesive force between a coating and a matrix and the corrosion resistance of the matrix are greatly improved.

Description

technical field [0001] The invention relates to the field of metal surface treatment agents, in particular to a chrome-free coating agent and a preparation method thereof. Background technique [0002] As we all know, hexavalent chromium will cause serious pollution to the environment. Its toxicity to the human body is also quite high, and half a tablespoon (about 2 ml) of a high-concentration hexavalent chromium solution can cause human death. Most products containing hexavalent chromium are irritating to the skin, eyes and mucous membranes, and it can also affect wound healing. From the perspective of occupational health, workers who work in high concentrations of hexavalent chromium mist have a higher chance of developing respiratory cancer. Because of these three reasons, European and American countries have carried out research on chromium-free substitution since the 1970s, and more and more industries are prohibited from using chromium-containing processes in the...

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Problems solved by technology

However, this patent has the following disadvantages: N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane accounts for too much in the formula composition, resulting in high product cost, resulting in a decline in market competitiveness and customer satisfaction degree drop

However, this patent has the following disadvantages: the proportion of aminopropyltriethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane in the formula composition is too large, resulting in high product cost and market competitiveness decline in customer satisfaction

However, this patent has the following disadvantages: the formula is an alkaline formula, which cannot form a dense film on the metal surface, but can only form an anti-rust water film, so it cannot be washed with water, which is far from meeting the requirements of the process

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