Types of Stainless Steel Fasteners and Environments

The Meaning of Stainless Steel

There is no doubt that stainless steel lives up to its name. The metal has the same strength as traditional steel and has excellent corrosion resistance over long useful lifetimes. Furthermore, there is an enormous variety of stainless-steel alloys available for all types of mechanical fasteners. Before proceeding, it is beneficial to first understand some fundamental stainless steel concepts.

The most basic definition of Stainless Steel 304 Bolts formed by combining an ordinary low carbon alloy steel with a “low” level of carbon, on the order of 0.3%-0.5%. As an alloying component, at least 10% Chromium has been added to this ordinary low alloy steel. The Chromium alloying element does all of the heavy lifting in terms of corrosion resistance and is the key component that distinguishes stainless steel.

The Benefits of Stainless Steel Fasteners

The primary advantage of Stainless Steel 304 Hex Bolts is that they protect the surface without the need for additional surface coatings or treatments. This means that stainless steel fasteners have a high degree of durability and corrosion resistance straight out of the box. These fasteners are as strong as traditional low alloy steel fasteners and can be used wherever traditional steel fasteners are specified. Stainless steel fasteners maintain good corrosion resistance over long useful lifespans, and as a result, they retain a glistening appearance for much longer than a traditional low alloy steel fastener.

Understanding the chemistry of how stainless steel fasteners resist corrosion is critical. The alloyed Chromium element in stainless steel reacts with oxygen in the air to form a metal-oxide layer on the exposed surface, which acts as an additional corrosion-protective layer. Surprisingly, if exposed to enough oxygen in its use environment, this layer can regenerate in some cases.

In this way, the oxygen molecularity re-bonds with newly exposed, accessible chromium inside the metal to reform the damaged protective surface layer. This brings up one more essential point: in order to maximize corrosion resistance of stainless steel fasteners, it is essential to make sure that the use environment contains at least some level of oxygen supply. This is simple in an open-air application, but it becomes significantly more difficult in more exotic applications, such as within oil or hydrocarbon fluid surroundings.

Two of the Most Popular Stainless Steel Fastener Alloys

In general, two types of stainless steel fasteners are most commonly used in machine designs. These two alloys are 304 and 316 stainless steel, and they are available in a variety of fastener sizes and specifications. Both alloys are from the 300 family of stainless steels, as their names indicate, but their mechanical properties differ due to their chemical composition.

Stainless Steel 304 Bolts is utilized more often than Stainless Steel 316 Bolts. It is composed of Chromium and Nickel. These alloying ingredients have high corrosion and oxidation resistance. As a result, 304 stainless steel bolt is widely used in piping, kitchen equipment, pressure vessels, and automobile parts.

316 stainless steel, on the other hand, is made up of similar Chromium and Nickel compositions. However, 316 stainless steel contains even more Molybdenum that is added specifically to protect against salt corrosion. As a result, 316 will offer higher resistance to corrosion in common environments known to be more corrosive than simple open areas, such as oceanic applications. When compared to 304 stainless-steel fasteners, the base material cost is more expensive to achieve this higher level of performance. 316 stainless-steel fasteners can be found in marine applications and other machine designs where fasteners may be exposed to exotic corrosive environments.

Selecting a Stainless Steel Fastener

The vast number of steel alloys and fastener designations can easily overwhelm you, but this guide should provide you with enough information to navigate the fundamentals of stainless-steel fasteners. It is also important to keep in mind that stainless steel is not completely corrosion-proof.

Types of Stainless Steel Fasteners and Environments

by Asiad Steels time to read: 3 min