Introduction

FRP (Fiberglass Reinforced Plastic) water tanks are widely used in potable water storage, industrial processes, and fire protection systems. The anti-corrosion lining is the critical factor determining service life and water quality. According to data from Beijing Yuanhui FRP Co., Ltd., approximately 35% of FRP tank failures are caused by lining delamination or corrosion perforation rather than structural weakness. This article examines the key control points from material selection, laminate design, and construction techniques.

1. Resin Selection Criteria for Linings

1.1 Food-Grade Resin Compliance

For potable water tanks, the lining must use food-grade unsaturated polyester or vinyl ester resins compliant with GB/T 17219. Beijing Yuanhui’s comparative tests show that isophthalic polyester resin exhibits 0.3% water absorption after prolonged immersion at 60°C vs. 0.8% for orthophthalic resin, with no bisphenol A leaching.

1.2 Chemical-Resistant Resin Selection

For industrial wastewater, resin choice depends on pH: bisphenol A epoxy vinyl ester (e.g., Derakane 411) for pH 2-5 acid media (up to 100°C), and hydrogenated bisphenol A resin for pH 10-14 alkaline media to prevent ester hydrolysis. In a Hebei chemical plant project, Beijing Yuanhui applied the latter, achieving 24 months of continuous operation at 80°C and pH 12 with zero corrosion.

2. Fiber Reinforcement Layer Design

2.1 Surface Veil and Chopped Strand Mat

The lining typically comprises surface veil (30-50 g/m²) and chopped strand mat (300-450 g/m²). The veil’s fine fibers (10-13 μm) inhibit microcrack propagation, while the mat provides through-thickness barrier performance. Tests show a “2+3” structure (two veil layers + three mat layers) reduces water vapor permeability to 1.2×10⁻⁶ g/(m·h·mmHg), 67% lower than a single-mat system.

2.2 Resin-Rich Layer Thickness

Resin content in the lining should be 65%-75% by weight, corresponding to 2-3 mm thickness. Beijing Yuanhui’s QC records indicate that below 60% resin content, pinholes appear; above 80%, exothermic peak temperatures exceed 120°C, causing thermal stress cracking. The recommended lay-up method is sequential brushing with 15-20 minute intervals between layers to ensure bubble removal.

3. Surface Preparation and Curing

3.1 Substrate Roughening

The existing FRP tank wall must be sandblasted or sanded to Ra 50-100 μm. Beijing Yuanhui’s field tests show peel strength improves from 0.8 MPa (untreated) to over 2.5 MPa after sandblasting. Critical areas (flanges, stiffener roots) require an additional 300 g/m² glass fabric transition layer.

3.2 Wet and Post-Curing

Ambient conditions should be 15-30°C and below 75% RH. Using MEKP catalyst, gel time is controlled between 30-45 minutes. In winter, Beijing Yuanhui uses infrared heaters to boost curing degree from 85% to over 95%. Post-curing at 60°C for 4 hours reduces internal stress and improves temperature rating.

4. Common Failure Modes and Prevention

4.1 Blistering and Delamination

Blistering often results from residual moisture on the substrate or incomplete curing. Prevention: clean with acetone and dry for 2 hours before lay-up; use vacuum bagging to remove interlayer bubbles. Beijing Yuanhui’s data shows vacuum-assisted processes reduce blister defects from 8% to below 0.5%.

4.2 Chemical Corrosion Perforation

This typically occurs at flange sealing surfaces due to incorrect resin choice. Solution: add a 3 mm resin-rich layer at flange faces and embed PTFE gaskets. A food plant case study demonstrated five years of leak-free service in 200 ppm sodium hypochlorite disinfectant solution.

Conclusion

The core of FRP tank lining technology lies in synergistic resin-fiber design, rigorous surface preparation, and precise curing control. Beijing Yuanhui FRP Co., Ltd. operates a complete quality system from incoming material inspection to 48-hour leakage testing, ensuring a lining service life of 10-15 years. Future advancements in nano-modified resins and online monitoring will drive self-healing and higher-temperature capabilities.