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.
In comparison, bolted steel storage tanks with factory powder coating have proven to be exceedingly durable due to the superior attributes of powder coating. Powder coating is flexible enough to endure impact without cracking and if the impact is extreme enough and the powder coating is compromised, the coating can easily be field repaired without taking the water storage tank out of service. After the repair, the bolted tank coating is completely intact once again and the repair blends in. As a secondary line of protection and to eliminate the spread of corrosion and coating undercutting, Superior Tank Co., Inc. adds our propriety SiZr seal. The SiZr seal is applied to the prepared steel under the powder coating to increase coating adhesion and to prevent corrosion.
An independent laboratory has proven the durability of our factory powder coating by performing a variety of rigorous tests including Taber abrasion testing and resistance to direct impact, temperature, corrosive salt spray and extreme humidity. In addition to withstanding these various tests, Superior Tanks have survived real life situations for decades.
The outstanding durability of our factory powder coating ensures our water storage tanks for fire protection and potable water storage will perform extremely well and survive the harshest conditions.