Trichloroacetic Acid Storage & Tank Compatibility

Storing Trichloroacetic Acid? Start Here

Trichloroacetic acid (C₂HCl₃O₂, CAS 76-03-9) is a strong, corrosive organic acid built from an acetic-acid backbone with all three methyl hydrogens replaced by chlorine. It ships as colorless, deliquescent crystals that pull water from the air and slump into a syrup, so it is almost always stored and dosed as an aqueous solution. In water it dissolves freely with a noticeable release of heat and ionizes strongly, giving a low pH that aggressively attacks metals and living tissue. Industrially it is used as a herbicide intermediate, a protein-precipitating reagent, an etchant and surface-prep acid, and a building block in fine-chemical synthesis. Because it combines genuine acid corrosivity with chloride content and a suspected-carcinogen profile, the right storage material is a real engineering decision rather than a default. The sections below give verified hazard data and an honest polyethylene verdict.

Is Trichloroacetic Acid Compatible with Polyethylene Tanks?

The honest answer is conditional. Polyethylene (HDPE and crosslinked XLPE) handles dilute, ambient-temperature aqueous trichloroacetic acid reasonably well, which is why it appears as acceptable on several chemical-resistance charts. But the resistance is not unconditional: published polyethylene charts note that the acid produces some effect after seven days of constant exposure and causes immediate damage near 122 deg F (50 deg C). As concentration and temperature rise, polyethylene moves from a fair rating toward unsuitable. For warm, concentrated, or long-residence storage, a fluoropolymer-lined tank or a rigid PVC/CPVC system is the more dependable choice. If you do use a poly tank, keep the solution dilute and cool, confirm the rating against your resin manufacturer's chart for your exact concentration, and validate every gasket, fitting, and vent material separately - those non-tank components are a common failure point with halogen-bearing acids.

Material compatibility at a glance

Trichloroacetic acid is a strong, corrosive, chlorine-bearing organic acid that is hygroscopic and handled almost entirely as an aqueous solution. For tankage, fluoropolymer-lined or rigid PVC/CPVC systems give the most reliable service; polyethylene (HDPE/XLPE) is a conditional choice that performs acceptably for dilute, ambient-temperature solutions but loses resistance as concentration and temperature climb. Stainless and carbon steel are unsuitable because the chloride-bearing acid pits and corrodes them. Match the wetted material to your exact concentration and storage temperature, and validate gaskets and fittings separately.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Causes severe skin burns and serious eye damage (H314/H318) - wear chemical-splash goggles, a face shield, and acid-resistant gloves and apron; have an emergency eyewash and safety shower within reach.
• Suspected carcinogen, mutagen, and reproductive hazard (H351/H341/H361) - minimize exposure, handle in well-ventilated or enclosed systems, and follow your site exposure-control plan.
• May cause drowsiness or dizziness and organ effects (H336/H371) - use local exhaust or respiratory protection to control mist and vapor from heated or concentrated solutions.
• Very toxic to aquatic life with long-lasting effects (H400/H410) - bund and contain all tankage; prevent any release to drains, soil, or surface water.
• Heating in the presence of water can decompose the acid and evolve hydrogen chloride and other toxic chlorinated gases - keep away from heat and incompatible reducing agents and bases.
• Corrosive to metals - never store in carbon or stainless steel; neutralize spills cautiously with a suitable base and dispose of as hazardous waste.

Common questions

What NFPA 704 rating does trichloroacetic acid carry?

It is rated 3-1-0: Health 3 (highly corrosive and toxic), Flammability 1 (combustible but not readily flammable, flash point above 230 deg F), and Instability 0 (stable under normal conditions). NOAA CAMEO lists the NFPA field as unavailable, but the published 3-1-0 diamond matches its corrosive, low-flammability, stable behavior.

Can I store trichloroacetic acid in an HDPE or XLPE tank?

Conditionally. Polyethylene is acceptable for dilute, ambient-temperature aqueous solutions but loses resistance as concentration and temperature increase, with charts noting damage near 122 deg F. For concentrated or warm service, choose a fluoropolymer-lined or PVC/CPVC system and verify against your resin maker's chart.

Why is stainless steel a poor choice for this acid?

Trichloroacetic acid is both a strong acid and chloride-bearing. That combination pits stainless steel and can drive chloride stress-corrosion cracking, so 304 and 316 are unsuitable for wetted storage. Fluoropolymer linings or rigid PVC/CPVC are the dependable alternatives.

What handling precautions matter most?

Treat it as a corrosive, suspected carcinogen, and aquatic toxin. Use splash goggles, face shield, acid gloves and apron with eyewash and shower nearby; control mist with ventilation; bund all tanks to prevent environmental release; and keep it away from heat that can drive off hydrogen chloride.