What chemical process is primarily responsible for oxygen corrosion in boiler systems?

The chemical process primarily responsible for oxygen corrosion in boiler systems is the electrochemical reaction between dissolved oxygen in the boiler water and the metal surfaces of the boiler. This reaction is an oxidation-reduction (redox) process where the metal, typically iron, is oxidized, meaning it loses electrons, and oxygen is reduced, meaning it gains electrons. The presence of dissolved oxygen in the boiler water causes the iron (Fe) in the boiler tubes and other components to react and form iron oxide (Fe2O3 or Fe3O4), commonly known as rust or magnetite. This reaction can be represented by simplified equations such as: 2Fe + O2 + 2H2O → 2Fe(OH)2, or 4Fe + 3O2 → 2Fe2O3. The electrochemical nature of the corrosion process means that it involves the flow of electrons between different locations on the metal surface, creating anodic (where metal dissolves) and cathodic (where oxygen is reduced) areas. The rate of oxygen corrosion is influenced by factors such as the concentration of dissolved oxygen, temperature, pH, and the presence of other dissolved salts. Higher temperatures generally increase the corrosion rate. Maintaining low levels of dissolved oxygen in boiler feedwater through mechanical deaeration and chemical oxygen scavenging is essential for preventing oxygen corrosion and ensuring the longevity and reliability of the boiler system.