While it is the most corrosion resistant metal available, there are several different corrosive elements that can occur with stainless steel if not used properly.
Five Corrosive Elements of Stainless Steel
The mechanical properties of stainless steel are what allows stainless structures to remain the most resistant to rust. Stainless steel contains a fine layer of chromium oxide that when breached or broken include natural techniques to self-repair. However, if the damage is too extensive the chromium oxide cannot repair its microstructure, and therefore corrosion occurs.
Harsh pitting corrosion is a localized damage that eats pits into stainless steel, usually caused by chloride ion, elevated temperatures for extended amounts of time, or lack of oxygen to the surface. Pitting is one of the most detrimental corrosive types. The only sure way to avoid it is to keep the steel away from prolonged exposure to these dangers.
#2 Crevice Corrosion
As with pitting, lack of oxygen can cause crevice corrosion to the steel’s surface. This particularly happens in the crevices of an object if not sealed off; hence the name. Crevice corrosion can take form between metal and metal or metal and non-metal materials.
#3 Stress Corrosion Cracking
Rare, yet severe, stress corrosion cracking is the result of tensile stress combined with elevated temperature, and moisture. At a highly increased rate, it is unlike that of other varieties. This type of decomposition can break down the mechanical properties of steel in days rather than months or years.
#4 Intergranular Attack
Another rare type of damage that can break down stainless structures is intergranular corrosion. The word “intergranular” as defined by dictionary.com is “located or occurring between granules or grains;” therefore, this corrosive harm happens between the grains. Chromium exposed to excessive heat, fuses with carbide, creating chromium carbide. Techniques used to avoid the problem of intergranular attack are using a low-carbon stainless steel or uniform heating and rapid cooling of the steel.
#5 General Corrosion
With not much penetration, but covering the entire surface, general corrosion can be quite destructive. Dissimilar of other corrosive damages, many of them are specific to locations that interact with whatever element is destructive. However, general corrosion happens to the entire surface consecutively. Usually, this type is due to the microstructure being permeated by an acid such as a sulfuric acid.
Stainless steel is the metal of all metals. While not completely corrosion-resistant, if chosen properly for the application, the right stainless alloy will last a lifetime. Let Stainless Structurals America help you avoid these harmful corrosive elements. Contact us today or visit our website for more details.