Choosing Stainless Steel Fasteners

The right stainless steel fasteners are essential to ensuring the longevity of your project. The chromium in stainless steel reacts with oxygen to create an inert layer that protects the metal from corrosion and can regenerate itself over time.

Grades of stainless steel differ in their ratios of chromium, nickel, molybdenum and carbon, which influences durability, resistance to high temperatures and other characteristics.

Durability

Stainless steel fasteners are long-lasting and provide superior load-bearing capabilities. They are also easy to install, low-maintenance, and aesthetically appealing.

Most fasteners used in construction applications are made of austenitic stainless steels such as grade 304 and 316. These grades are known for their durability in high moisture levels and chemical exposure.

The alloyed Chromium in these fasteners creates a layer that protects the exposed surfaces from corrosion. The protective layer even regenerates if damaged. Additionally, these stainless fasteners resist hydrogen embrittlement.

However, some stainless-steel fasteners have a brushed, satin or rougher finish which may trap minute particles that damage the protective layer. This can result in tea-staining which causes the stainless to look rusty or dull. This can be reduced by electro-polishing or passivating which improves corrosion resistance.

Corrosion Resistance

When choosing fasteners, it’s important to consider the material they’re made from. Different materials provide different characteristics and benefits. For instance, stainless steel fasteners offer corrosion resistance.

Stainless steel contains chromium, which creates a passive layer on the surface that stops oxygen from contacting the base metal and prevents corrosion. This is what makes it stand out from other metals.

Grades such as 304 and 316 are commonly used for projects that will encounter saltwater or chloride-rich environments. These grades have a higher chromium content than other stainless steels and are more resistant to corrosion.

For less severe applications, 410 stainless steel is often used for roofing screws or self-tapping screws. Compared to 18-8, it’s less resistant to corrosion but still holds up well in most atmospheres. It’s also magnetic, unlike most stainless steels. Fasteners of this variety are popular for use in cladding systems and rainscreens. They’re also work hardening, which helps reduce thread failure.

Aesthetics

In addition to their durability and corrosion resistance, stainless steel fasteners also offer good aesthetics. They do not rust and can keep their appearance for a long time, making them attractive to builders, manufacturers and homeowners alike.

Stainless steel is an alloy that contains iron and more than 10 percent chromium. The chromium gives stainless steel an oxide layer, which is not reactive and acts as a passive barrier against corrosive materials. This means that stainless steel fasteners are resistant to alkaline and acidic substances, as well as saltwater.

Galvanized steel is another popular fastener material, but it is not as corrosion-resistant as 316 marine grade stainless steel. Additionally, galvanized fasteners do not resist crevice corrosion. Alternatively, you could choose silicon bronze, which is an alloy that combines copper, tin and silicon. However, silicon bronze does not have the classic metal aesthetic of stainless steel and it is more expensive than 316 stainless steel. It is best used when corrosion resistance is a priority, but visual appeal is not essential.

Installation

The type of stainless steel fastener chosen will affect how well it performs. Depending on the application or environment, different head and thread types might be needed. For example, hex heads can offer more torque resistance than socket head versions. And, the choice of driving recess design can also make a difference.

Grade is also a critical factor. For instance, austenitic grades – commonly referred to as 304 and 316 – are good in many environments. They offer high corrosion protection for a fair price. However, they do not have the strength of heat treated carbon steel.

If an environment has harsh chemical exposure, consider using martensitic or precipitation-hardened grades with a higher molybdenum content. These grades will offer increased corrosion resistance against calcium brines, hypochlorite solutions, sodium, phosphoric acid and sulfurous acids.