THE PROBLEM
The glass fused steel tank was heavily perforated and leaking effluent into the surrounding environment.
Glass Fused Steel Tank Lining Wrexham
THE SOLUTION
Glass fused steel tanks are a challenging tank lining application with intricacies that many others overlook and an area that we have researched extensively. We proposed the use of two of our linings which have proven results for the is challenging application.
Glass fused steel is marketed as an extremely durable solution, however whilst the finished surface offers good chemical resistance, this does not tell the full story. More information on this can be found here.
Following draining down and cleaning by the client all of the existing sealant was removed to expose the panel edges and bolt areas as these areas can be particularly prone to corrosion due to some manufacturers not coating this area with the glass enamel coating.
Once this had been removed the tank was thoroughly cleaned by method of steam cleaning using an emulsifying degreaser to remove fats and greases present and also soluble salts. The effectiveness of this washing was confirmed by conducting a soluble slats test as per ISO 8502.
The importance of removing surface contaminants before preparing for the application of a tank lining cannot be understated. If fats, oils and grease are present they can be forced further into the substate during abrasive blasting, something that would prevent the proper adhesion of the new tank lining. Soluble salts if left in place will lead to osmotic blistering, where by moisture is drawn through the coating film.
Following cleaning all surfaces were prepared by method of abrasive blasting, preparing any exposed steel to SA2.5 as per ISO 8501-1. The surface roughness / blast profile was tested and recorded using a surface profile needle gauge as part of our standard tank lining quality assurance.
Abrasive blasting exposed the full extent of the perforations in the tank, which were severe. This were focused solely in the gas space due to the presence of hydrogen sulphide in this area. All surfaces were vacuumed clean and the effectiveness of this confirmed as per ISO8502-3. Ensuring all surfaces are dust free prior to coating application ensures proper adhesion of the new tank lining, as if not the new tank lining will be adhered to dust rather than the desired substrate.
Dehumidification and heating was introduced to reduce the humidity in order to prevent flash rusting and ensure the correct climatic conditions for tank lining application. This was tested and recorded as part of our standard tank lining quality assurance.
All surfaces were primed using Corrolast DSP – our primer specifically designed for lining Glass Fused to Steel tanks. This primer has excellent adhesion to even smooth glass without abrasive blasting. The primer also contains a mined pigment that converts any corrosion present to stable iron oxides such as magnetite.
All perforations in the tank were sealed using galvanised steel plates bonded into place using a thixotropic epoxy adhesive.
The gas space of the tank was the lined using SPI Corrolastic HT pure polyurea tank lining at a thickness of 2mm. This material is both extremely high tensile and elastomeric, making it particularly suitable for lining glass fused to steel / bolted tanks. The high tensile nature means that it effectively forms a ‘tank within a tank’. This means that whilst the bonded plates are sealing the perforations, they are actually working more akin to a scaffold supporting the polyurea tank lining.
The lower section of the tank was then lined using Corrolast Tank Guard – a flexible and crack bridging epoxy tank lining specifically designed for waste water and effluent applications. This was applied in two coats of contrasting colour as per best tank lining practice to a thickness of 800 microns.
All bolts received a separate heavy stripe coat to ensure full tank lining thickness in areas where tank linings pull thin through gravity and surface tension.
As part of our standard tank lining quality assurance dry film thickness readings were taken and a spark test conducted. When undertaking tank linings in aggressive waste water environments a single pin hole is a point of failure which will allow moisture and aggressive chemicals to reach the steel substrate, allowing corrosion to commence once again.
Finally all pipe penetrations and termination points were sealed using a polyurethane jointing compound specifically designed for waste water and effluent applications.