Corrosion-Resistant Alloy (CRA)

What Does Corrosion-Resistant Alloy (CRA) Mean?

A corrosion-resistant alloy is a type of metal or alloy that has been designed to resist corrosion when exposed to a corrosive environment, such as water, acids or alkalis.

Corrosionpedia Explains Corrosion-Resistant Alloy (CRA)

Corrosion-resistant alloys are engineered to have specific properties that make them resistant to corrosion. These properties include high levels of chromium, nickel, or other alloying elements that form a passive oxide layer on the surface of the material, which protects it from further corrosion. Additionally, these alloys may have a specific microstructure, such as precipitation-hardened or duplex structures, that enhances their resistance to corrosion.

Some common examples of corrosion-resistant alloys include:

• Stainless steel. This is a type of steel alloy that contains at least 10.5 percent chromium, which forms a passive oxide layer that protects the underlying material from corrosion.
• Inconel. This is a family of nickel-based alloys that are highly resistant to corrosion and high-temperature environments. Inconel alloys are commonly used in the aerospace and chemical industries.
• Hastelloy. This is a family of nickel-molybdenum alloys that are highly resistant to corrosion and are commonly used in the chemical processing industry.
• Titanium alloys. These alloys are highly resistant to corrosion, especially in seawater environments. They are commonly used in marine applications, such as offshore oil rigs.

The selection of a corrosion-resistant alloy is quite complex and depends on the specific application and the type of corrosive environment to which it will be exposed. Improper selection of CRAs can result in application errors, unreliable results and a lower life expectancy for the asset. For best results in CRA selection, it's recommended to develop and implement a testing program which simulates the conditions of a particular field environment. From there, testers can narrow down a group of potential candidates and test them a few at a time to determine the best CRA for the application.

Factors such as temperature, pressure and exposure time must also be considered during the selection process.