Anthony Porreco
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Why are some hex nuts blue in color?
It is often asked why some high strength hex nuts that are supplied with high strength bolts appear to be blue or some other color. This is normally the case with galvanized, high strength, heavy hex nuts and the reason for this is because of the wax lubricant applied to the nuts. According to the ASTM A563 specification, “Hot-dip and mechanically deposited zinc-coated Grade DH nuts shall be provided with an (…)
via American Fastener Journal – SEPTEMBER/OCTOBER 2016 : Waxed Nuts.