Hoden Seimitsu Kako Kenkyusho Co., Ltd.

Kengo Takase

Yasuhiko Endo

Tomio Sakai

Shunjiro Watanabe

Shoichiro Adachi

Provided is a chromium-free surface treatment method which imparts practical rust inhibitive performance to a metal product having a zinc surface to which it was difficult to impart rust inhibitive performance of practical level. A conversion-coated film of zinc phosphate etc. is formed on the zinc surface of the metal product as pretreatment, and the silica-based film is formed by applying a chromium-free surface treatment agent which uses alcohol or mixture of water and alcohol as a solvent to the conversion-coated film. As a result, when an aqueous surface treatment agent containing alcohol is applied, it is possible to suppress the formation of white rusting for 72 hours or longer in the salt spray test.

Chromium-free rust inhibitive treatment method for metal products having zinc surface and metal products treated thereby

Provided is a chromium-free rust inhibitive paint for metals which is obtained by mixing a flaky zinc powder into a water reducible binder solution containing a water reducible resin emulsion and a water soluble silane coupling agent. A thin film of a silane compound having a hydrophobic group is added to particle surfaces of the flaky zinc powder, whereby the flaky metallic zinc powder exhibits water repellent property. When a surface treatment agent which contains an alkoxysilane oligomer as an essential component is applied to the paint film of a rust inhibitive paint for metals, this extends the time until red rusting occurs on painted metal products to not less than twice and prevents white rusting and black rusting for a long time. Rust inhibitive performance is further improved by blending a nano-sized powder of titanium dioxide, polyvinyl butyral, a silane coupling agent, etc., with the surface treatment agent.

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Kasugai, Japan

Kengo Takase