Stainless Steel for Corrosion resistance

WHAT IS CORROSION?

Corrosion is the degradation of a material (usually a metal), or its properties, as a result of exposure to environmental conditions. This degradation is the outcome of a chemical reaction known as oxidation in which, characteristically, electrons are given up by the atoms of the base metal. A familiar example of metal corrosion is rust, which is a result of iron or steel oxidation due to moisture in the atmosphere.

The level of corrosion a material experiences depends on the severity of the environmental conditions and the amount of time the material is exposed. Degradation, of some degree, is inevitable, but some metals are more susceptible to oxidation than others. Different industries and applications present different risks of exposure to harsh chemicals, extreme temperatures, corrosive fluids, and environmental elements. Choosing the correct metal for the application, as well as taking additional precautions, can help lessen the effects of corrosion.

Corrosion occurs in two types of environments:

• Aqueous (Wet) — corrosion most commonly occurs through electron transfer in moist environments. Oxygen-rich atmospheric moisture, saltwater, or other liquids such as acids or chemical cleaners serve as an electrolyte, enabling a base metal anode to oxidize (lose electrons) to a cathode. The oxidation can result in one or more types of degradation to the base metal including crevice corrosion, pitting, intergranular corrosion, stress corrosion, galvanic corrosion, etc.
• Gaseous (High-Temperature) — High-temperature corrosion, though comprising a small percentage of electrical industry applications, takes place in areas such as furnaces, turbines, and engines where metal comes into contact with hot gases and contaminants. Almost all metals oxidize once they reach highly elevated temperatures, often forming oxide scales on the surface.

In electrical systems, the service life of components such as conduit and fittings typically depends on the type of metal selected. Many metals can fall victim to the effects of corrosive elements. Some of the more common corrosive elements include:

• Sulfur dioxide and sulfuric acid
• Ammonia
• Chlorine and chlorides
• Salts
• Water

To combat these harmful substances, many installers are turning to the resiliency of stainless steel.

STAINLESS STEEL SOLUTIONS

An alternative to coated steels (e.g., hot-dip galvanized), PVC, and aluminum, stainless steel offers improved resistance against common corrosives. Stainless steel’s inherent advantage comes from the presence of chromium (at least 10.5%) which causes a thin, passive, film layer to form on its surface in oxidizing environments. If the metal’s surface is scratched and the film layer is disturbed, the chromium exposed to the atmosphere will immediately re-form a protective layer to defend against further oxidation. Additional alloying elements such as nickel, and molybdenum in Type 316 SS, further enhance film formation and corrosion resistance. This can be very beneficial in certain environments such as those containing chlorides.

Stainless steel offers superior corrosion resistance compared to the formerly popular zinc-plated, galvanized, and carbon steels — materials that have low initial overhead expenses but costly maintenance and replacement fees. The long service life of stainless steel — 10-20 times longer than carbon steel or iron in the same working environment — makes it the best overall choice to defend against the harmful effects of corrosion.

The success of your application can hinge on material selection. Gibson Stainless manufactures stainless steel products that address corrosion challenges while offering easy installation and minimal maintenance and repair.

To learn more about our stainless steel selection, visit our catalog or contact us today.