Silane-class chromium-free passivating agent and preparation method thereof

Abstract

The invention relates to a silane-class chromium-free passivating agent and a preparation method thereof. The silane-class chromium-free passivating agent is prepared from the following raw materialsincluding, by weight, 25-35 parts of organosilane, 5-10 parts of a corrosion inhibitor, 5-10 parts of phytic acid, 5-10 parts of glutinous rice flour, 1-3 parts of a crosslinking agent, 10-20 parts ofnano silica, 3-5 parts of a dispersing agent, 100-200 parts of water and 750-850 parts of alcohol. The preparation steps are that after the glutinous rice flour is screened with a 200-mesh sieve, theraw materials are weighed according to the weight, the alcohol and the water are uniformly mixed firstly, then the organosilane, the corrosion inhibitor, the phytic acid and the crosslinking agent are sequentially added to be stirred to be dissolved, the glutinous rice flour is slowly added with the rate being 20 mL / min while stirring is carried out, stirring is continuously carried out for 30 min, then the nano silica and the dispersing agent are added, and a mixture is evenly stirred and dispersed. The silane-class chromium-free passivating agent is environment-friendly and free of chromium, a passivation film is thick, the adhesive force is good, and the corrosion resistance is good.

Description

technical field [0001] The invention belongs to the technical field of galvanizing, and in particular relates to a silane-based chromium-free passivator and a preparation method thereof. Background technique [0002] Hot-dip galvanizing is the most commonly used protective cathodic protection method for cold-rolled steel sheets, but the galvanized layer is easily corroded in the air (especially in humid air). In order to prevent the corrosion of the galvanized layer, passivation treatment is required. The traditional passivation method is to coat the surface of the hot-dip galvanized steel sheet with a hexavalent chromium passivation agent, and form a passivation layer containing hexavalent chromium salt after drying. , but hexavalent chromium is toxic and carcinogenic, which not only affects human health, but also easily causes harm to the environment, and it will be gradually eliminated by the market. The ROHS directive issued by the European Union clearly restricts the u...

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Problems solved by technology

[0003] In the existing chromium-free passivating agent, silane molecules can be hydrolyzed in alcohol and aqueous solution to form a certain number of silanol groups (SiOH), which react chemically at the interface between silane and metal to form metal silicon Oxygen bonds (SiOMe), silanol groups that do not participate in chemical reactions form a colloidal silane film structure SiOSi network structure, the above structure can effectively prevent the intrusion of aggressive media on the one hand, and on the other hand can form a stable film layer , this feature makes organosilane passivation treatment an important research direction in recent years; however, the disadvantage of silane passivation is that the passivation film formed is thin, easy to damage, and has no self-healing ability, which limits its application

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