Polyurea Coating for Digester Tank
Introduction
A water utility client's anaerobic digester tank had developed water and gas leakage alongside chemical degradation to the interior lining. External walls showed active carbonation-induced corrosion. Full removal of the existing coating system was required, with replacement by a chemical-resistant, gas-tight lining across both internal and external surfaces.
Our Solution
Surface preparation was carried out to NACE/SSPC-SP13 standard. Tank internals were high-pressure water jetted at 18,000+ psi to remove laitance and debris, followed by abrasive blasting to eliminate residual coating, a water-based degreaser application, and a final high-pressure wash. New concrete casting had introduced surface voids; these were addressed using a rotary diamond wheel to grind high spots, followed by spray-applied polymer resurfacing compound to restore a uniform substrate profile.
Internally, a monolithic pure polyurea coating was spray-applied, providing a flexible, chemical-resistant, gas-tight membrane. Externally, a three-layer anti-carbonation system — primer plus two heavy topcoats — was applied at 5,000 psi post-jet, delivering waterproofing, elongation capacity, and long-term resistance to carbonation-driven degradation.
Key Benefits
- Gas-tight integrity restored — monolithic polyurea eliminates water and gas permeation pathways
- Chemical resistance — pure polyurea provides robust protection against aggressive digester chemistry
- Surface voids eliminated — polymer resurfacing compound ensured a continuous, defect-free bond surface
- Carbonation protection — three-layer exterior system prevents further concrete degradation
- Elongation capacity — coating flexes with structural movement, reducing risk of cracking or delamination
- Preparation to NACE/SSPC-SP13 — verified surface cleanliness for maximum adhesion performance
- Extended service life — system designed to significantly reduce maintenance frequency and tank downtime
Conclusion
UCL Ltd returned the digester tank to full operational integrity through a correctly specified, rigorously prepared polyurea coating system. This project demonstrates our capability to specify and apply high-performance protective coatings in demanding wastewater environments to recognised international standards.
Our services.
The disciplines behind work like this — browse by what you need.
Industrial Coatings
UCL Ltd delivers industrial coatings through Ultimate Coatings, protecting tanks, pipework, concrete and structural steel against corrosion and chemical attack.
Civils & Mechanical Engineering
Mechanical installations and civil engineering works delivered by one accountable contractor, from design to completion.
Concrete Repair & Anti-Carbonation Coatings
UCL Ltd repairs and protects concrete infrastructure showing cracking, spalling or carbonation damage, restoring structural integrity without full replacement.
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