CASE STUDY
WASTEWATER INLET TANK REPAIR
Belzona Repairs and Protects Tank Damaged by Chemical Attack
Industry: Water and Wastewater
Application: Repair and Chemical Coating Protection
Products: Belzona 4301 (Magma CR1 Hi-Build), Belzona 4311 (Magma CR1), Belzona 9341 (Reinforcement Tape)
Customer Location: : WA, Australia
Application Date: June 2026
PROBLEM
Inspection of a wastewater inlet tank identified severe damage and leakage caused by chemical attack from hydrogen sulphide gas released above the waterline.
Previous attempts had been made to seal leaks on the side of the tank with silicone. Because the tank could not be emptied for inspection, it was very difficult to ascertain the degree of damage.
When we gained access to the interior of the tank to commence repairs, the extent of the corrosion was found to be far greater than anticipated. Along one side of the tank, approximately nine metres of the surface contained numerous holes, some large enough to fit a hand through. The discharge outlet pipe had also suffered severe corrosion.
Wastewater inlet tank damaged by chemical attack caused by hydrogen sulphide and requiring repair
Previous silicone leak repairs on the tank exterior
Silicone removed, revealing severe corrosion and numerous holes
Corroded discharge outlet pipe prior to repair
Previous silicone leak repairs on the tank exterior
More Information?
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APPLICATION
The original repair scope involved cold bonding steel plates to the tank exterior. After the true extent of the damage was revealed, it was decided that the best repair method would be to apply Belzona 9341 incorporated with Belzona 4301, as this would be quicker and easier to conform around the ridges running down both sides of the tank.
In addition, two coats of Belzona 4311 were applied, which, together with Belzona 4301, would provide long-term resistance to the chemicals present within the wastewater treatment environment.
Tank exterior after abrasive blasting
Blasted interior revealing nine metres of holes
Close up of holes in water tank
Stage 1: High pressure wash the interior of the tank.
Stage 2: Abrasive blast to SA2.5 to achieve a minimum surface profile of 75 micron.
Stage 3: Apply two layers of Belzona 9341, fully wetted out with Belzona 4301, over all holes on the tank interior.
Stage 4: Apply two 300-micron coats of Belzona 4311 to provide long-term chemical protection.
Stage 5: Apply a further two layers of Belzona 9341, fully wetted out with Belzona 4301, over all holes on the tank exterior. This creates a four-layer reinforced repair system across each damaged area.
Stage 6: Apply a four-layer system of Belzona 9341, fully wetted out with Belzona 4301, over all holes in the discharge outlet pipe.
Belzona 9341 being wetted out with Belzona 4301
Positioning wetted-out Belzona 9341 over the damaged areas
Additional Belzona 4301 applied over the reinforced repair
Completed nine-metre internal repair section
First coat of Belzona 4311 (Red)
Second coat of Belzona 4311 (Grey)
Completed repair to the tank exterior
OUTCOME
The Belzona repair and coating system was a major success and took a total of ten days to complete. Due to the low temperatures, the tank remained offline for a further six days to achieve full chemical cure. The customer was very satisfied with the quality of the application and the final result. Crucially, the repair saved thousands of dollars compared with replacing the tank, which would have taken months to fabricate and install.
Products
Belzona 4301 (Magma CR1 Hi-Build)
A durable, two-parts repair composite for long-term metal and concrete protection from a broad range of chemicals, especially concentrated inorganic acid and alkalis (e.g. nitric acid, sulfuric acid, sodium hydroxide).
Belzona 4311 (Magma CR1)
A durable, 2-part epoxy coating for the long-term protection of concrete and metal surfaces from chemical attack. This solvent-free coating isolates concrete and metal surfaces from aggressive chemicals especially acids and alkalis. It is easy to mix and apply by hand or spray without the need of specialist tools and cures at room temperature.
About Rezitech
Established in 1968, Rezitech is the sole Australian Distributor for Belzona. Rezitech offers a comprehensive range of industrial protective coatings and epoxy metal repair composites to many different industries including: oil and gas, mining, power, water and waste water, pulp and paper, marine, manufacturing among others.
Frequently asked questions
What caused the wastewater inlet tank to corrode and leak?
The tank suffered severe chemical attack from hydrogen sulphide gas released above the waterline. Approximately nine metres of one tank wall contained numerous holes, while the discharge outlet pipe was also severely corroded.
How was the severely corroded wastewater inlet tank repaired?
The damaged areas were repaired using Belzona 9341 Reinforcement Tape fully wetted out with Belzona 4301. Layers were applied internally and externally to create a four-layer reinforced repair system over the holes, with the discharge outlet pipe repaired using the same method.
How was the tank prepared before the Belzona repair was applied?
The tank interior was high-pressure washed and abrasive blasted to SA2.5, achieving a minimum surface profile of 75 microns. This provided a clean, profiled surface for the reinforced repair and protective coating system.
How was the wastewater inlet tank protected against future chemical attack?
After the structural repairs were completed, two 300-micron coats of Belzona 4311 were applied to provide long-term chemical protection. Belzona 4301 and Belzona 4311 were selected for their resistance to aggressive chemicals found in wastewater treatment environments.
What were the benefits of repairing the wastewater tank instead of replacing it?
The Belzona repair and coating system restored the existing tank and saved the customer thousands of dollars. It also avoided the months that would have been required to fabricate and install a replacement tank.
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