Introduction

FRP water tanks are widely used in municipal water supply, industrial cooling, and fire protection systems. The anti-corrosion performance of the inner lining directly determines service life and water quality safety. Based on over a decade of field data from Beijing Yuanhui FRP Co., Ltd., more than 60% of tank failures originate from lining corrosion or interface delamination. This article examines the core technical aspects of lining anti-corrosion.

1. Material Selection and Matching

1.1 Resin System Criteria

The lining typically uses bisphenol-A unsaturated polyester resin or vinyl ester resin, with a thickness of 2-4mm. For media with chloride ion concentrations exceeding 500ppm (e.g., coastal groundwater), vinyl ester resin is recommended—its chemical resistance outperforms standard polyester by 3-5 times. In a chemical plant project in Hebei, Beijing Yuanhui applied vinyl ester lining, and the tank operated in circulating water with pH 2-12 for 5 years without any corrosion spots.

1.2 Reinforcement Layering

The lining comprises a composite structure: surface veil (30-50g/m²) to prevent micro-crack propagation, chopped strand mat (450g/m²) for impact buffering, and E-glass woven roving (800g/m²) for structural strength. The layer sequence must not be reversed to avoid stress concentration.

2. Construction Process Control

2.1 Mold Surface and Release Agent

Mold surface roughness should be Ra≤3.2μm. Use PVA release agent or semi-permanent release wax. In a Shandong project, uneven release wax application caused local lining adhesion and rework, delaying the schedule by 3 days. Spray application is recommended with a thickness of 15-25μm.

2.2 Curing and Post-Treatment

Cure the lining at 20-30°C and humidity ≤75%, with a curing degree ≥90% before next steps. Use infrared thermography to monitor exothermic peak temperature, keeping it below 80°C to prevent resin degradation. A water plant project adopted segmented curing, extending curing time from 8 to 12 hours, increasing Barcol hardness from 35 to 42.

3. Quality Inspection and Acceptance

3.1 Non-Destructive Testing

Use spark testing (5kV/mm) to detect pinholes and micro-cracks; leakage density should be ≤0.1 points/m². Ultrasonic thickness gauges verify lining thickness with a tolerance of ±0.2mm.

3.2 Chemical Immersion Test

Per GB/T 3857, specimens are immersed in 60°C media for 168 hours. Weight change ≤0.5% and flexural strength retention ≥85% are required. Beijing Yuanhui’s internal standard mandates no blistering, cracking, or discoloration after immersion.

4. Engineering Case Studies

4.1 Case 1: Coastal Power Plant Cooling Water Tank

A Shandong power plant used seawater cooling. The original polyester resin lining developed widespread blistering after 18 months due to chloride ion penetration causing glass-resin interface failure. After switching to vinyl ester resin with three layers of surface veil, continuous monitoring for 36 months showed no anomalies.

4.2 Case 2: Food-Grade Pure Water Tank Retrofit

A Beijing food plant converted a carbon steel tank to an FRP lining, requiring effluent conductivity ≤5μS/cm. Beijing Yuanhui used food-grade unsaturated polyester resin with 2% nano-silica to enhance density. Final effluent conductivity stabilized at 3.2μS/cm.

Conclusion

Successful FRP tank lining anti-corrosion relies on material compatibility, precise process control, and closed-loop quality verification. Owners should request complete material corrosion reports, construction records, and third-party test data from suppliers. Beijing Yuanhui FRP Co., Ltd. offers full-service technical support from material consultation to on-site inspection, ensuring long-term project performance.