Protective coatings are the most widely used corrosion control technique. Essentially, protective coating materials are a means for separating the surfaces that are susceptible to corrosion attack. Another method, cathodic protection, interferes with the natural action of electrochemical cells that are responsible for corrosion. Cathodic protection can be effectively used to resist corrosion of surfaces that are immersed in water or exposed to soil.
Corrosion resistance is an important factor to consider when selecting materials for corrosion control. The materials most resistant to corrosion are those for which corrosion is thermodynamically unfavorable. Some metals have naturally slow reaction kinetics, even though their corrosion is thermodynamically favorable. These include metals such as zinc, magnesium and cadmium.
Thus, a material's own resistance to corrosion or protective methods to arrest corrosion fall under the category of corrosion resistance.
Subscribe to our newsletter to get expert advice and top insights on corrosion science, mitigation and prevention. By: Della Anggabrata. Dictionary Dictionary Term of the Day.
Corrosionpedia Terms. Anodize This: The Brilliance of Anodizing. Top Corrosion Mitigation Technologies to Watch for in Soluble Salts and Coating Performance.
However, many people do not realize what a stainless steel is comprised of, what types are available, the environments it is effective and the environments in which it is less effective. Stainless steels are carbon steels , typically a low carbon steel , that have higher amounts of chromium. The addition of chromium is part of the reason for their corrosion resistance. Stainless steels also frequently have other corrosion-resistant alloying elements, such as nickel or molybdenum, added to them.
Not only do these elements have an effect on corrosion resistance, but they also play a role in the mechanical properties, thermal properties and even the magnetism of a stainless steel. The measure of alloying for resistance to corrosion MARC is an equation used to measure the susceptibility of various alloys to corrosion.
Because there are so many different combinations of alloying elements that can be used in stainless steel, there are many different grades and types.
Stainless steels can be divided into three main families: austenitic, ferritic and martensitic. While there are other groups, these three are typically considered the most widely used. Austenitic stainless steels are extremely corrosion-resistant.
Like all stainless steels, they are comprised of a carbon steel make up with a high addition of chromium. This nickel acts as an austenite promoter, meaning that it causes the steel to have an austenitic face-centered cubic crystalline structure. They are generally the most expensive of the three. Common applications include food preparation equipment, medical devices and process vessels subjected to immersion in water. Ferritic stainless steels, while still corrosion-resistant, are less so than their austenitic counterparts.
They too have high amounts of chromium, but do not have the nickel that austenitic stainless steels possess. This reduces their ability to reduce corrosion, but it does give them an edge with some mechanical properties such as formability. Ferritic stainless steels are also more affordable than austenitic stainless steels. Ferritic stainless steels are commonly used for automotive components such as exhaust systems and for heat exchangers.
Martensitic stainless steels are also generally less corrosion-resistant than austenitic stainless steels. Martensitic stainless steels have high amounts of chromium, sometimes have additions of nickel, and have a higher carbon content than austenitic or ferritic stainless steels. This allows them to be heat treatable and have a much higher strength and hardness than ferritic or austenitic stainless steels.
Martensitic stainless steel is used for tooling and cutlery. As with all of the metals listed in this guide, corrosion-resistant does not mean corrosion-proof; under the right conditions, stainless steel corrosion can occur.
For more about stainless steels, read An Introduction to Stainless Steels. Aluminum is another corrosion-resistant metal that is frequently used in applications subject to harsh environments.
Aluminum is corrosion resistant because when its surface is exposed to oxygen, it forms an aluminum oxide layer on the aluminum's surface. The aluminum oxide is actually more durable than the aluminum itself, thus protecting the remaining aluminum. Compare this to iron oxide, or rust, which flakes off and allows more iron oxide to form.
Aluminum is frequently used in the aerospace industry for airplane body components. The ability of aluminum to resist corrosion makes it attractive to the aerospace industry because it reduces the amount of overhaul that must be performed due to corrosion. Aluminum is also used extensively in the food and beverage industry, where its corrosion resistance makes it less likely to contaminate food.
Even if the zinc coating is scratched off, it continues to protect nearby areas of the underlying steel through cathodic protection, as well as by forming a protective coating of zinc oxide. Like aluminum , zinc is highly reactive to oxygen in the presence of moisture, and the coating prevents the iron in the steel from further oxidation.
Industrial Metal Supply carries a wide range of rust-resistant metals for a variety of applications. Industrial Metal Supply is the Southlands largest supplier of all types of metal and metalworking accessories , including rust prevention products. Contact Us.
Posted in: stainless steel , Brass , Galvanized , copper , aluminum. Time to Read: 2m 30s. Aluminum metal Many aircraft are made from aluminum , as are car and bike parts. Galvanized Steel Galvanized steel takes a long time to rust, but it will eventually rust. All aluminum Steel stainless steel copper Brass Contact Us. Los Angeles. Sitemap Contact Us.
0コメント