We Don’t Crack Under Pressure!

We Don't Crack Under Pressure! (glass)

In the bolted steel tank industry, two coating options are common; factory powder coating and glass-fused-to-steel coating. Each of the coatings has its own unique properties and characteristics when applied to bolted tanks and steel tanks for water storage.

Bolted tanks with a glass-fused-to-steel coating are attractive to potential buyers as the coating is non-porous and very rigid. The glass is applied directly to the steel then heated to 1500˚F to melt the glass and bond the glass to the steel. In theory, the glass coating isolates the steel from the liquids stored in the bolted tank. Unfortunately, the real world can be very different from theory. Ironically, the same properties which make the glass coating attractive for use with water storage tanks also make the coating vulnerable to cracking. The rigidity of the coating does not allow the glass to flex with the steel tank panels which expand and contract with temperature changes. This difference in expansion rates can lead to the coating cracking under stress. In addition, the extreme rigidity of the glass coating can help to resist very minor impacts but can lead to cracking if impacted with any significant force. When the coating on a glass-lined bolted tank cracks, the steel underneath is exposed and corrosion will likely occur. After the corrosion starts to spread, it can result in undercutting and the overall failure of the coating. As the glass coating is applied to the steel at the factory and melted at a very high temperature, it is not possible to fully repair a bolted tank with a glass-fused-to-steel coating. The only “fix” possible is to cover the cracked area with mastic. The proper way to ensure the panel does not experience corrosion and coating failure is to replace the entire damaged panel as glass-lining cannot be fixed or repaired in the field. The vulnerability of a glass-lined tank to impact makes it critical to protect the storage tank panels during shipping and installation as well as after the ground storage tank is installed. A dropped tool or thrown rock can result in an expensive repair and require the storage tank to be taken out of service to replace an entire panel.

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