What Does Cold Wall Effect Mean?
Cold wall effect refers to a condition where a structure - such as a tank, vessel, building, etc. - has a lower atmospheric temperature on the outside than the product that is stored inside the structure. This condition can exist in structures that have coatings/linings. Cold wall effect can damage the structures, leads to the premature failure of linings of structures, and results in unplanned downtime, repair or replacement costs, and safety and environmental issues.
Corrosionpedia Explains Cold Wall Effect
The cold wall effect occurs when there is a temperature gradient that exists between the inside and outside of structures. Normally, hot liquid inside the tanks or vessels creates this condition. If the interior and exterior temperatures were different, the hot liquid would permeate the tank lining at a significantly high rate. The greater temperature gradient causes faster permeation. When the hot liquid permeates any salt deposits on the steel, corrosion cells will form and grow. This temperature gradient and permeation cause blisters in the lining, which finally rupture and expose the steel to chemicals and oxygen in the tanks or vessels.
The cold wall effect is a significant challenge to linings and coatings used to protect steel surfaces (tanks, piping and vessels) that are exposed to liquid at elevated temperatures, generally above 100°F. This effect is also seen in ships' tanks where the contents exist at a higher temperature gradient than the ambient temperature. It also commonly occurs in process vessels where a process liquid is running significantly higher than the ambient temperature.
The cold wall effect can be minimized by washing and rinsing the surface with clean, fresh, potable water before final surface preparation with sufficient profile. The removal of soluble salts from the steel surface is also a prime concern to protect corrosion in the steel structures. Thick-film linings such as rubber or elastomeric polyurethane also help to reduce the temperature gradient between the exterior and interior of the tank. Polyurethane foam insulation can be used on the outside of the tank. The blend of carbon steel tanks and well-engineered linings can provide the most cost-effective solution to reduce cold wall effect on structures.