Introduction

FRP water tanks are widely used in municipal water supply, industrial fluid storage, and fire protection systems. The anti-corrosion performance of the inner lining directly determines the tank's actual service life. According to the industry standard JC/T 658.1-2018, the three core indicators for composite linings are chemical resistance, impermeability, and adhesion. Beijing Yuanhui FRP Co., Ltd. has found in two decades of production that over 70% of early failures originate from design or installation defects in the lining layer. This article provides actionable anti-corrosion solutions covering materials, processes, and inspection.

1. Resin Selection: Matching the Medium

1.1 General vs. Speciality Resins

For drinking water tanks, food-grade isophthalic polyester resin (e.g., DS-300 series) must be used, with residual styrene below 0.5% as per GB/T 17219-1998. For industrial acid storage (e.g., 10% sulfuric acid), bisphenol-A epoxy vinyl ester resin (e.g., Derakane 411-350) is recommended, offering temperature resistance up to 100°C and an oxygen permeability rate below 0.02 mm/year. In a Hebei chemical plant project, Beijing Yuanhui applied vinyl ester lining on a 300 m³ tank, which has operated for 8 years without leakage.

1.2 Cure System and Working Window

For ambient-temperature application, MEKP/cobalt naphthenate system is used, with gel time controlled at 25–35 minutes (25°C). In winter, add N,N-dimethylaniline accelerator to reduce gel time to below 15 minutes, preventing sagging or micro-porosity from incomplete curing.

2. Reinforcement Layer Design: Balance of Impermeability and Strength

2.1 Thickness and Fiber Architecture

The anti-corrosion lining typically comprises three layers: surface veil (0.3–0.5 mm), chopped strand mat (1.0–1.5 mm), and woven roving structural layer (2.0–3.0 mm). Beijing Yuanhui lab tests show that when total thickness falls below 2.5 mm, leakage probability rises to 0.8% under 0.6 MPa hydraulic cycling (100,000 cycles). Recommended minimum total thickness: ≥3.0 mm for drinking water tanks, ≥4.5 mm for chemical tanks.

2.2 Interfacial Treatment

Substrate (steel or concrete) must be abrasive-blasted to Sa2.5 with surface roughness Rz ≥70 μm. The primer should be a mixture of vinyl ester resin and 3–5 wt% nano-silica, achieving interlayer shear strength above 18 MPa. In a Xiong'an New Area pumping station project, Beijing Yuanhui applied blasting + primer, resulting in pull-off strength of 6.2 MPa (standard requirement ≥4.0 MPa).

3. Critical Process Control

3.1 Ambient Conditions and Interlayer Interval

Working area temperature: 10–30°C, relative humidity below 75%. Each resin layer must reach 70% cure before the next ply (tack-free test: no stickiness, no indentation). Beijing Yuanhui quality records show that insufficient interval time accounts for 42% of delamination defects.

3.2 Pinhole Repair

For pinholes >0.5 mm diameter, drill to 2 mm using a conical bit, fill with high-thixotropic resin putty (thixotropic index ≥5.0), cure and sand smooth. Spark testing at 5 kV/mm must pass 100%. In 2023, Beijing Yuanhui repaired a 150 m³ food factory tank, achieving zero spark breakdown after repair.

4. Quality Inspection and Maintenance Cycle

4.1 On-line Testing

After lining completion, conduct a 24-hour full water test; deformation should not exceed 0.3%. Barcol hardness (ASTM D2583) must be ≥40. For drinking water tanks, an additional 72-hour immersion followed by water quality test is required, with TOC increase ≤2 mg/L.

4.2 Regular Maintenance

Perform an endoscopic inspection every 12 months, focusing on weld heat-affected zones and pipe connections. Beijing Yuanhui client data shows that tanks receiving annual maintenance last 5–7 years longer. If local blistering or discoloration is found, excise and repair immediately to prevent corrosion from spreading to the structural layer.

Conclusion

FRP water tank lining anti-corrosion is a system engineering process, requiring closed-loop control from resin selection, laminate structure, construction technique, to inspection and maintenance. Beijing Yuanhui FRP Co., Ltd. recommends that buyers request a detailed anti-corrosion design calculation and historical project data from suppliers. Only by combining technical standards with field experience can a 20-year-plus design life be achieved.