What Does Gouging Mean?
Gouging is a type of corrosion that occurs on a metallic surface in which a hole, groove or indentation is created. Gouging happens in boiler tubes because of caustic corrosion that occurs as a result of excessive use of alkalines such as sodium hydroxide (NaOH). This can lead to caustic gouging and stress corrosion cracking.
Corrosionpedia Explains Gouging
Gouging happens mostly in the carbon steel tubes at the joints or the U bend sections in waste heat boilers. The carbon steel tubes experiences the metal wastage in the form of caustic corrosion gouging, which tends to make a hole or indentation in the bend sections. Similarly, stainless steel tubes are failed because of caustic induced stress corrosion cracking. Also, when alkalines such as sodium hydroxide carry over moisture with them, this causes gouging, which gets further aggravated if silicon and sulfur are also present as they form sulfates and silicates.
Corrosion due to caustic gouging can be repaired or maintained by performing mechanical techniques such as grinding of the damaged surface, then milling, routing and chipping. Once this is done, either of the two common methods of gouging metal can be used for repair works
- Plasma gouging or
- Air carbon arc welding