The amount of metal removed from a pipe wall is _________ to the magnitude of the current flowing in the corrosion cell.

• A. The amount of metal removed
• B. The rate of corrosion
• C. The thickness of the pipe wall
• D. The rate of disintegration

Answer: (A)

Current flow in a corrosion cell is the driver of metal dissolution. According to Faraday’s law, the amount of metal that dissolves is proportional to the total electric charge that has passed, and charge equals current times time (Q = I · t). The mass removed can be expressed as m = (M/nF) · Q, where M is the metal’s molar mass, n is the number of electrons per atom, and F is Faraday’s constant. So, for a given time, more current means more charge passes and more metal is removed; overall, the amount of metal removed is proportional to the current magnitude (and time). This is why the answer emphasizes the relationship between metal loss and current. The thickness of the pipe wall or the rate of disintegration aren’t the direct quantity described here, and while the rate of corrosion is related to current, the statement specifically refers to the total amount removed.