Any penetration through the protective layer will render the screw vulnerable to rust. 4 The plating on the fastener is rapidly consumed, leaving the bare fastener metal. Unfortunately, all of these metals and alloys are vulnerable to corrosion. Screws, of course, are typically made of metals and alloys, some of which include steel, aluminum and brass. 3 The corrosion of the base metal is considerably increased by the fastener. Corrosion Protection Both galvanization and zinc-plating offer a high level of protection against corrosion. 2 The corrosion of the base metal is marginally increased by the fastener. This makes them more prone to surface penetration. Plating Compatibility Chart KEY: 1 The corrosion of the base metal is not increased by the fastener.
Produces a passive corrosion-resistant finish.Īcid dip produces a hard oxide surface. Zinc-Plated Screws A zinc-coated screw uses electricity to apply the zinc, which means the protective layer is thinner than a galvanized screw. Parts are dipped in nitric acid which removes iron particles and brightens the finish. Size must be adjusted to allow for thickness of coat. Hard lustrous finish adds wear resistance and is very expensive. Hard stable finish, relatively expensive and sometimes hard to apply. Black Oxide: Black: Ferrous metals and stainless steel: Fair: A chemical discoloration which does not add to part thickness. Olive drab, green, black, red, blue, bronzeĪpplied on top of zinc or cadmium plating as a die for color and additional corrosion protection. Zinc & cadmium plated parts: Very good: A secondary dipping process after plating increasing corrosion resistance, adding color or brilliance. Low cost.Ĭhemically produced coating superior to regular phosphate and oil. Zinc or manganese phosphate used with a rust-inhibiting oil dip. Relatively high cost and toxic to the environment.Ī secondary dipping process after plating increasing corrosion resistance, adding color or brilliance.Ī chemical discoloration which does not add to part thickness. Fasteners that have been zinc plated and clear passivated. Superior rust-resisting qualities used in marine and aviation applications. Zinc plated fasteners will rust if placed in a wet environment and are not suitable for outside use. Good rust-resisting qualities, appearance and low cost. Common fastener platings and finishes and their characteristics. You'll find all of the popular platings and finishes at Fastener Mart. Refer to the chart below for other options. Chromium (chrome), although expensive, is used when a bright hard finish is desired especially when the fastener is visible. Hot dip galvanized is very resistant to corrosion, but its finish is somewhat irregular and, consequently, unpleasing. Zinc is the most common because of its pleasing appearance, low cost and good rust resistance. Platings and finishes affect not only how a fastener looks, but also how it will withstand corrosion-deterioration of the metal-caused by exposure to the weather or chemicals.
#Do zinc plated bolts rust series#
Fastener Tech Data | Understanding Series Introduction
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