What are the two general causes of corrosion?

What are the two general causes of corrosion?

• A. Wear from mechanical abrasion
• B. Electro-chemical attack and direct chemical attack
• C. Fatigue and creep
• D. Thermal oxidation and wear

Answer: (B)

Corrosion happens when a metal reacts with its surroundings in a way that causes material loss. There are two broad pathways: electrochemical attack, where the metal forms anodic and cathodic sites in a conductive electrolyte and electrons flow through the metal, driving oxidation at the anode; and direct chemical attack, where the metal is chemically attacked by oxidizers or other agents in the environment without the need for an electrochemical circuit. For example, iron rusting in moist or salty environments is electrochemical corrosion, while iron dissolving in a concentrated acid is direct chemical attack. The other options describe wear or mechanical degradation rather than these chemical/electrochemical processes, or mix in a specific condition (like high-temperature oxidation) that isn’t capturing the two general pathways.

Corrosion happens when a metal reacts with its surroundings in a way that causes material loss. There are two broad pathways: electrochemical attack, where the metal forms anodic and cathodic sites in a conductive electrolyte and electrons flow through the metal, driving oxidation at the anode; and direct chemical attack, where the metal is chemically attacked by oxidizers or other agents in the environment without the need for an electrochemical circuit. For example, iron rusting in moist or salty environments is electrochemical corrosion, while iron dissolving in a concentrated acid is direct chemical attack. The other options describe wear or mechanical degradation rather than these chemical/electrochemical processes, or mix in a specific condition (like high-temperature oxidation) that isn’t capturing the two general pathways.