Stainless Steel Enclosures in Industrial Applications

July 8, 2009
Stainless steel is a versatile material known primarily for its strength and corrosion resistant properties and utilized in the construction of enclosure solutions that satisfy applications across a broad spectrum of industries. While a wide assortment of different components are housed within these enclosures and placed in disparate environments, there are common criteria that must be considered to ensure that the proper stainless steel enclosure is chosen for a given application.

This paper explores some of the technical details of stainless steel that are crucial to the selection of industrial enclosures including composition, distinguishing properties of different grades, chemical resistances, suitable applications and general benefits offered by stainless steel when compared to carbon steel enclosures.

What Exactly Is Stainless steel?

By definition, stainless steel is a metal alloy containing at least 10.5% chromium by mass. In a process known as passivation, the chromium within the metal forms a very thin layer of chromium oxide when exposed to the oxygen in our atmosphere. This layer continually protects the metal beneath and spontaneously regenerates if the surface is scratched which is why stainless steel enclosures provide excellent corrosion resistance without the need for painting or any kind of surface treatment. It is because of this passivation that stainless steel alloys do not display the gross surface rusting common in carbon steel alloys. If the passivation layer is destroyed beyond repair, however, corrosion will occur in the form of localized pitting.


The American Iron and Steel Institute (AISI) first classified certain types of stainless steel as standard compositions and designated each type with a 3-digit number. AISI no longer maintains these standards, but the Society of Automotive Engineers International (SAE) and ASTM International (the American Society for Testing and Materials) have since filled this role. In addition, new designations were created utilizing the Unified Numbering System (UNS), which consists of one letter and five numerals and the DIN standard, established in Germany and common to Europe, which uses five numerals and no letters.
SAE grade 304 stainless steel is comprised of 18-20% chromium and 8-10.5% nickel. This is the standard type of stainless steel used in the enclosure industry—filling the widest range of applications. Limitations of type 304 stainless steel include use in outdoor applications near large bodies of saltwater where airborne salt can come into contact with the surface of the enclosure. A rule of thumb is that type 304 stainless steel should not be used within 5 miles of the coast, but the true distance at which corrosion can occur is dependent upon local weather patterns. Cold climate regions where chlorides are used as de-icing agents may also cause significant pitting in type 304 stainless steels. For these reasons, type 304 stainless steel is not recommended in these situations without a regular cleaning regimen.