|
Corrosionist The Website of Corrosion and Corrosion Control |
| You are here >>> Corrosion Prevention Home - Corrosion Rust FAQ - What Causes Rust | ||
What Causes Rust |
||
| How does rust form | What is Corrosion | Corrosion Pictures | Metal Corrosion |Copper Pipe Corrosion | Galvanic Corrosion | Chemistry of Corrosion | Define Oxidation | What is Oxidation | Introduction to Welding | ||
|
|
||
|
What Causes Rust Electrochemical corrosion is the most important mechanism that causes Rust. Four conditions must exist before electrochemical corrosion can proceed: (1) there must be something that rusts , the metal anode, where the oxydation reaction take places (2) there must be a cathode, where the reduction reaction take places (3) there must be continuous conductive liquid path (electrolyte, usually condensate and salt or other contaminations), for example: water, seawater, condensing water, humidity.. (4) there must be a conductor to carry the flow of electrons from the anode to the cathode. This conductor is usually in the form of metal-to-metal contact such as in bolted or riveted joints. The elimination of any one of the four conditions will remove the conditions that causes rust. An unbroken (perfect) coating on the surface of the metal will prevent the electrolyte from connecting the cathode and anode so the current cannot flow. Therefore, no rust will occur as long as the coating is unbroken. |
||
|
|