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Zinc flake coatings are non-electrolytically applied coatings, which provide good protection against corrosion. These coatings consist of a mixture of zinc and aluminium flakes, which are bonded together by an inorganic matrix. The specifications for zinc flake coatings are defined in international standard ISO 10683 and also in European standard DIN EN 13858. DIN EN ISO 10683 sets out the requirements for zinc flake coatings for threaded fasteners and DIN EN 13858 describes the requirements for zinc flake coatings for fasteners with no thread and for other parts as well. There are three groups of zinc flake coatings: # Zinc flake coatings containing Cr(VI) (hexavalent chromium): surfaces containing Cr(VI) provide greater anti-corrosion protection with a thinner coating, but Cr(VI) is carcinogenic and poses a potential risk to the environment. New European decrees prohibit the use of surfaces containing Cr(VI). These include the Vehicle End-of-Life Directive EC 2000/53 as of 1 July 2007 and directive EC 2002/95 on electrical and electronic equipment (the RoHS Directive). For applications outside of the automotive and electrical industries these coatings are still valid. # Solvent based Cr(VI)-free zinc flake coatings. # Water based Cr(VI)-free zinc flake coatings. Cr(VI)-free coatings are more environmentally friendly than surfaces with a Cr(VI) content. No zinc flake coatings used in the automotive industry nowadays contain this substance. Various manufactures, such as car companies and their suppliers, have produced their own specifications and supply rules in order to define the requirements for these coating systems. Zinc flake coating is a generic term for the coating technology and this is marketed by the different suppliers under their respective brand names. The companies generally act as licensors for the individual coating businesses. == History == Because electrolytically zinc-plated surfaces provide comparatively little corrosion protection, and in the case of galvanic zinc coatings on high-strength steel (e.g. category 10.9 and 12.9 high-strength bolts) there is a risk of hydrogen embrittlement, the industry needed a better corrosion protection system. High-strength steel parts (such as bolts of strength category > 10.9 and nuts of > 9) and components with tensile strength of > 1000 N/mm2 or > 320 HV are susceptible to hydrogen embrittlement. Galvanic coating processes and pickling with acids have a major influence on the development of hydrogen-induced brittle fractures. In the 1970s, a new coating system was developed in the United States: zinc flake coating (patent number 1376067). By virtue of a thin coat thickness of typically 8-12 µm this system produced a high level of protection against corrosion and made it possible to avoid hydrogen embrittlement. In the 1980s and ‘90s, the use of these coating systems spread, e.g. within the automotive industry. This industry needs coating systems offering a high level of corrosion resistance. As zinc flake coatings do not create any hydrogen in the process, they were used for critical applications as an alternative to electroplating. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Zinc flake coating」の詳細全文を読む スポンサード リンク
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