What metal type should the fastener be?
Fasteners hold our world in place, from the baby's nappy to the zip on your jeans, to the bolts in your car chassis. They’re designed to hold materials together, and they come in many forms. See What screw do I use?, What nail do I use? and What bolt, nut and washer do I use?
Think about the location of the fastener. Will it be joining materials indoors, in a wet area (in the bathroom), or in a dry area (in a bedroom)? Will it be fastening materials outdoors? Does it need to be rust resistant?
Fasteners are made from various metals for strength, pliability or anti-corrosion purposes. No metal, except gold and platinum in its natural state, is completely corrosion resistant. Fasteners, therefore, may be coated for extra corrosion or rust protection. Here is a basic list for basic needs.
Steel nails, screws and bolts are graded for strength. Grade 2 is the standard hardware grade and is the least expensive. Grades 5 and 8 are more highly tempered for more specialised strength uses. Steel fasteners are usually plated with a silver or yellow zinc coating or galvanised to resist rust.
A zinc coating provides better corrosion resistance. Fasteners that have been zinc plated have a shiny silver or golden appearance, referred to as ‘clear’ or ‘yellow’ zinc respectively. They’re fairly corrosion-resistant but will rust if the coating is destroyed or if exposed to a marine environment.
Galvanising is another coating involving the application of a layer of zinc. Hot-dipped galvanising puts the thickest possible coating on the metal, resulting in superior corrosion resistance. Use it outdoors, in marine environments and with highly treated
outdoor timber where chemicals can be quite corrosive.
If you want the shiny look, use a chrome-plated fastener. Chrome is used in plating fasteners for its appearance. It provides similar corrosion resistance to zinc plating, but its main drawback is the extremely high cost. If more corrosion resistance is required, you could use a stainless steel fastener plated in chrome. If the plating is scratched or
penetrated, the stainless steel will deter further corrosion.
Stainless steel is a highly corrosion-resistant alloy. No plating is needed on a stainless steel fastener as the corrosion resistance is inherent in the structure. Though more expensive than plated steel, it is the metal of choice for outdoor jobs and most marine
Alloy steel bolts are made from a high-strength steel alloy and are further heat treated than Grade 8 steel. Typically they aren’t plated, resulting in a dull black finish. They’re
extremely strong but very brittle.
Silicon bronze, often referred to simply as bronze, is an alloy made mostly of copper and tin with a small amount of silicon. Bronze is used mainly in marine environments. It is preferred over stainless steel in wooden boat construction because of its superior corrosion resistance, and preferred over brass because of its higher strength. Bronze is
similar in colour to copper and is also sometimes seen in fine woodworking, where it is used for its appearance. The main drawback of bronze is its high cost.
Brass is a copper and zinc alloy. It is highly corrosion-resistant and electrically conductive. However, its use as a fastener is rather limited because of its relative softness. It is used mainly for its appearance.
An alloy consisting of approximately 95% zinc alloyed with aluminium, copper and other elements for good corrosion resistance. It isn’t very strong compared to steel.