API 571 Certification (Corrosion & Materials) Practice Test

What type of stress corrosion cracking (SCC) is associated with carbon steel and low alloy steels?

1. Chloride SCC

2. Carbonate SCC

3. Sulfide SCC

4. Hydrogen SCC

The correct answer is: Carbonate SCC

Carbonate stress corrosion cracking (SCC) is particularly relevant to carbon steel and low alloy steels primarily due to their susceptibility to certain environments, such as those containing bicarbonates or carbonate ions. In these scenarios, the presence of water along with carbonate species can lead to the formation of a localized environment that promotes SCC. For carbon and low alloy steels, the mechanism of SCC involves the electrochemical processes that occur when these materials are exposed to specific conditions, often involving stress, a corrosive environment, and a sufficient concentration of carbonates. Such cracking can lead to significant failures in structural integrity, making it crucial to understand the environments that can lead to this type of SCC, especially in industries such as oil and gas, where these materials are commonly utilized. Other forms of SCC, such as those associated with chloride, sulfide, or hydrogen environments, could affect various alloys differently but are less characteristic of carbon steel and low alloy steels specifically in the context of carbonate environments.