API 571 Certification (Corrosion & Materials) Practice Test

What is a primary factor in concentration cell corrosion sensitivity?

1. Material grade

2. Particle size

3. Alloy composition

4. Temperature fluctuations

The correct answer is: Alloy composition

Concentration cell corrosion occurs when there is a difference in concentration of the electrolyte, leading to an electrochemical cell where areas of higher concentration are more cathodic and areas of lower concentration are more anodic. This differential can create localized corrosion, particularly in metals. The primary factor influencing concentration cell corrosion sensitivity is alloy composition. Different alloying elements can impact the electrochemical behavior of the material in the presence of varying environmental conditions and concentrations. The specific interactions of those alloying elements with the electrolyte can significantly influence the material's potential and, consequently, its susceptibility to localized corrosion. Material grade, particle size, and temperature fluctuations can also play roles in corrosion behavior, but they do not specifically address the fundamental mechanisms of concentration cell corrosion as directly as alloy composition does. For instance, material grade can influence general corrosion resistance but does not inherently dictate the cell characteristics driving concentration cell corrosion. Similarly, while temperature variations may affect reaction rates, they do not fundamentally change the concentration-driven nature of the corrosion process. Lastly, particle size may influence the overall surface area of a material, but this factor is more relevant to general corrosion rather than the specific dynamics of concentration cells.