A guide to chemical-resistant tank linings: epoxy, epoxy novolac (98% acid), vinyl ester (acids/alkalis/solvents, high temperature), immersion surface prep, holiday testing, and standards API 652 / NACE SP0178 / SP0188 — selecting by chemical and temperature for work in Thailand.
Storage tanks — acid, alkali, oil, fuel, water, chemicals — corrode "from the inside" continuously while holding liquid, far harsher than external corrosion. Ordinary external anti-rust paint cannot be used for immersion — it requires a dedicated tank lining (chemical-resistant internal coating).
This article explains lining types, selection by chemical, surface prep, holiday testing, and the API 652 / NACE standards.
1. Why Immersion Is Harsher Than the Exterior
flowchart TD A[Steel surface inside tank] --> B[Submerged in liquid continuously
immersion service] B --> C[Chemical permeation] B --> D[High concentration + temperature] B --> E[Abrasion from agitation/flow] C --> F[Needs special chemical-resistant resin
+ thicker + 100% holiday test] D --> F E --> F
- Permeation — chemicals diffuse through the film to the steel if the lining is thin/wrong type
- Concentration + temperature accelerate corrosion
- A single pinhole = liquid reaches steel = perforating corrosion
2. Lining Types — Choose by Chemical
| Lining | Resists | Temperature | Application |
|---|---|---|---|
| Epoxy | general chemicals | medium | general water/fuel tanks |
| Epoxy Novolac | concentrated acids (H₂SO₄ to 98%) | ~95-130°C | acid/oil/mild-solvent tanks |
| Vinyl Ester | broad acids+alkalis+solvents | high + abrasion | aggressive chemicals/high temp (6-40 mils) |
| Rubber / Glass-flake | specialized acid/abrasion | per system | special work |
Choose by the manufacturer's chemical resistance chart against the actual chemical + concentration + temperature.
3. The Heart — Surface Prep + Holiday Test
- Immersion surface prep is more rigorous — abrasive blast Sa 2.5+ and correction of surface imperfections (sharp edges, welds, porosity) per NACE SP0178
- 100% holiday test (NACE SP0188) — inspect the whole surface for pinholes with a high-voltage spark (thick linings) or wet sponge (thin linings) — one holiday fails it
- DFT per lining spec (immersion needs more thickness than atmospheric work)
Unlike external work which tolerates minor imperfections — immersion must be 100%.
4. Standards
- API 652 — lining of aboveground oil-storage tank bottoms
- NACE SP0178 — surface prep/weld detailing for immersion lining
- NACE SP0188 — holiday/discontinuity testing
- ISO 12944 (Im category) — immersion · NACE SP0181 — internal coating
5. Tank Lining Spec Checklist
- State chemical + concentration + temperature in the tank (sets the lining choice)
- Select the resin from the chemical resistance chart (novolac/vinyl ester)
- Specify surface prep (Sa 2.5+, correct surface imperfections per NACE SP0178)
- Specify DFT + 100% holiday test (NACE SP0188)
- Food/drinking water → certified lining for food/water contact
We supply and coordinate chemical-resistant tank linings — epoxy, epoxy novolac (concentrated acids), vinyl ester (aggressive chemicals/high temperature) to API 652 / NACE SP0178 / SP0188 — with guidance on selecting the resin by actual chemical + temperature, immersion surface prep, and 100% holiday testing for acid/fuel/water/food tanks.
Talk to our engineering team to select a lining system that fits your chemicals — call 02-096-2118 or LINE OA @sahawatt1988.
Summary
- Tank lining ≠ external paint — immersion is harsher (permeation + concentration + temperature + abrasion)
- Epoxy novolac (concentrated acids ~95-130°C) · Vinyl ester (broad acids/alkalis/solvents, high temp)
- Choose by the chemical resistance chart (chemical + concentration + actual temperature)
- Surface prep Sa 2.5+ (NACE SP0178) + 100% holiday test (SP0188) — a single pinhole fails
- Standards: API 652 / NACE SP0178 / SP0188 / ISO 12944 Im
The right lining type + complete holiday testing = no tank leaks/contamination, where repair + downtime cost many times more.
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Frequently Asked Questions
1How does tank lining (internal) differ from external anti-rust paint?
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2Epoxy Novolac or Vinyl Ester — which to choose?
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3Why is holiday testing so critical for tank lining?
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4Which Thai applications need tank lining?
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