| Chemical Corrosion | Electrochemical Corrosion |
|---|---|
| It occurs in dry conditions. | It occurs in wet conditions such as presence of electrolyte or moisture. |
| It takes place by direct chemical attack of atmospheric gases such as O2, CO2, Cl2, H2S, SO2. | It takes place by electrochemical attack of corrosive environment on the surface of metal. This involves setting up of a large number of galvanic cells. |
| It takes place on homogeneous and heterogeneous metal surfaces. | It takes place on heterogeneous metal surfaces only. |
| Corrosion product is formed at the place of corrosion. | Corrosion takes place at anode but corrosion product is formed near cathode. |
| Corrosion is uniform. | Corrosion is non-uniform. When anodic area is small, pitting corrosion takes place more frequently. |
| It is a slow process. | It is a fast process. |
| It involves chemical reactions of atmospheric gases. | It involves electrochemical reactions. |
