Methods to prevent corrosion

Methods to prevent corrosion

1. Material selection

   • development of new alloys
   • monitoring the surface condition

2. Environmental alteration

   • limiting contact with rain or seawater
   • methods to reduce sulfur, chloride or oxygen content in the surrounding environment
   • ex: treat feed water for water boiler with softeners

3. Design consideration

   • Avoid sharp corners
   • complete draining of vessels
   • no water retention
   • avoid contact between dissimilar metals
   • avoid sudden changes in section
   • weld rather than rivet
   • easy replacement of vulnarable parts
   • avoid excessive mechanical stress

4. Coating

   • paints and other organic coating are used to protect metals from the degradative effect of environmental gasses.
   • common organic coatings:
     • water-soluble coatings
     • high-solid coatings
     • powder coatings

5. Anodic protection

   • Anodic protection involves coating the iron alloy steel with a less active metal, such as tin

6. Cathodic protection

   • Cathodic protection protects against galvanic corrosion
   • Cathodic protection works by converting unwanted anodic (active) sites on a metal's surface to cathodic (passive) sites through the application of an opposing current
   • has two forms
     • sacrificial system
     • impressed current protection