Introduction

The anti-corrosion lining of FRP water tanks determines their service life. In 2019, a chemical plant suffered a $170,000 loss due to lining failure. Beijing Yuanhui FRP Co., Ltd. has developed a systematic anti-corrosion technology based on 15 years of engineering experience. This article covers material selection, construction processes, and quality inspection.

1. Material Selection: Resin and Reinforcement Compatibility

1.1 Resin Systems

Vinyl ester resin (VE) is recommended for acidic or chlorine-containing media (pH 2-5), with a crosslinking density 30% higher than orthophthalic polyester. In a seawater desalination project, Beijing Yuanhui used VE lining, achieving 92% Barcol hardness retention after 3 years of immersion, versus 78% for UPR.

1.2 Reinforcement

Surface mat (30-50g/m² C-glass) ensures a resin-rich layer (>85% resin content) to block capillary penetration. Structural layers use 450g/m² E-glass woven roving, with resin wet-out time controlled at 8-12 seconds. Optimized layering reduced permeability to 5×10⁻¹² cm/s.

2. Construction Processes: Hand Lay-Up and Spray-Up

2.1 Hand Lay-Up

For complex shapes, hand lay-up requires gel time control: at 25°C, add 1.5% MEKP and 0.5% cobalt naphthenate to achieve 40-50 min gel time. Bubble content must stay below 0.5%. In a pharmaceutical project, Beijing Yuanhui achieved 2.5±0.3mm lining thickness with zero pinholes.

2.2 Spray-Up

Spray-up is efficient for flat surfaces: spray distance 35-40cm, gun speed 0.5-0.8m/s, single pass thickness 0.3-0.5mm. Humidity must be <75% to avoid blushing. In a power plant project, Beijing Yuanhui sprayed 150m² per day with >98% cure degree.

2.3 RTM (Resin Transfer Molding)

For high-performance tanks, RTM controls fiber content at 35-45% with injection pressure 0.2-0.5MPa and resin viscosity 300-500mPa·s. RTM linings showed 40% longer chemical resistance than hand lay-up in semiconductor applications.

3. Corrosion Environment Adaptation and Barrier Layer Design

3.1 Media-Specific Solutions

For potable water, food-grade epoxy resin complying with GB/T 5750 standard is used (free phenol <0.1mg/L). For 80°C hot water tanks, 15% graphite filler is added to raise thermal conductivity to 0.8W/(m·K), preventing thermal stress cracking.

3.2 Barrier Thickness Calculation

Per ASTM C581, barrier thickness t = (P·d)/(2σ). With P=0.3MPa and d=crack width, Beijing Yuanhui designed 6mm barrier for a 2m³ tank, passing 100,000 fatigue cycles without leakage.

4. Quality Inspection and Acceptance

Post-construction tests include: Barcol hardness (≥40), spark testing (5kV/m, no breakdown), and hydrostatic test (1.5× working pressure, 24h). Beijing Yuanhui provides third-party reports for each tank, with 100% pass rate in 2022.

Conclusion

Effective FRP tank lining requires integrated resin selection, process control, and inspection. Beijing Yuanhui recommends VE resin + RTM for aggressive media, and food-grade epoxy + hand lay-up for drinking water. Properly constructed linings achieve >15-year service life with <2% repair rate.