Comparison between Glass Lined Tank and Epoxy Coated Tank
Unlike other coating system which sit on the steel surface, our glass is fused to steel at over 830°. The result is fusion of two materials to become a single composite material.
What many still be surprising is how the composite has the strength and flexibility of steel combined with the corrosion resistance of glass, but with little of the usual brittleness of glass. This is because as the steel cools following fusion the glass is placed under compression and remains under compression even when the steel flexes. Glass is at its strongest under compression.
The finished plate exhibits the characteristics of a true composite material in which the fine glass matrix relieves stresses and prevents crack propagation.
If we take an even closer look at the glass/steel boundary we can see that the glass and the steel have truly fused together forming a highly keyed interface which makes for a very strong physical bond between the two components (left image).
Compare this with a factory applied epoxy coating at the same magnification and you can see how striking the difference is. Both of these cross sections are magnified by 2000 times using Electron Microscopy (right image).
If you look closely at the typical epoxy/steel boundary you will even see a gap between the coating and the steel clearly showing a point where there is no bonding at the epoxy/steel interface which can be a potential source of blistering. The electron micrograph below shows the epoxy cross section at a magnification of 5000 times.
These observations corroborate laboratory findings that the adhesion of Glass to Steel is far greater than the adhesion of epoxy to Steel.
In experiments designed to pull the glass away from the steel we have found that it is usually the bond between the applied load and the glass which breaks before the glass can be separated from the steel.
In practice this means that Glass-Fused-to-Steel is better able to withstand the rigours of the construction site and provide a long life even in abrasive and chemical environments.
By contrast epoxy paint is a soft material which continues to cure for some time after application, even when factory applied. Running the edge of coin across the surface will usually reveal its inherent weakness. Great care has to be taken when handling epoxy coated sheets at the slightest scratch can provide a route for liquid to track along the steel/epoxy interface allowing corrosion to progress unhindered. It is not surprising that earlier attempts to launch epoxy coated tanks into the European market have been a commercial failure. With paint based system, it is not a question of if you have to re-paint but, when and how often.