When temperature increases, the corrosion rate usually ________, and when the water is corrosive and the velocity increases, the corrosion rate ______?

When temperature increases, the corrosion rate usually ________, and when the water is corrosive and the velocity increases, the corrosion rate ______?

• A. Increases, increases
• B. Decreases, decreases
• C. Decreases, increases
• D. Increases, decreases

Answer: (A)

Increasing temperature speeds up electrochemical reactions and diffusion, so corrosion rate tends to rise as temperature goes up. In a corrosive water environment, higher flow velocity boosts mass transfer of aggressive species to the metal surface and can physically remove protective films, lifting the barrier to corrosion. Together these effects mean the corrosion rate increases in both cases, so the best choice is that both rise.

Increasing temperature speeds up electrochemical reactions and diffusion, so corrosion rate tends to rise as temperature goes up. In a corrosive water environment, higher flow velocity boosts mass transfer of aggressive species to the metal surface and can physically remove protective films, lifting the barrier to corrosion. Together these effects mean the corrosion rate increases in both cases, so the best choice is that both rise.