Monochloroacetic Acid (MCAA) Storage & Tank Compatibility

Storing Monochloroacetic Acid (MCAA)? Start Here

Monochloroacetic acid (MCAA), formula C₂H₃ClO₂, is a colorless-to-white crystalline solid and one of the haloacetic acids. It is a strong, corrosive organic acid widely used as a chemical building block to make carboxymethyl cellulose, glycine, thioglycolic acid, herbicides, surfactants and pharmaceutical intermediates. In water it dissolves readily to form an acutely toxic, corrosive solution. The compound is hazardous by every route of exposure - it is fatal in contact with skin or if inhaled, toxic if swallowed, and causes severe skin burns and eye damage. It is also very toxic to aquatic life. Because dilute aqueous MCAA solutions are routinely stored and metered in industrial settings, polyethylene tanks are a common containment choice when the concentration and temperature stay within the resin's published limits. Strict engineering controls, secondary containment and corrosion-resistant wetted components are essential for safe handling.

Is Polyethylene (HDPE / XLPE) Compatible With Monochloroacetic Acid?

Yes - for aqueous monochloroacetic acid solutions at ambient temperature, polyethylene rates compatible (S) on the major resin chemical resistance charts. High-density polyethylene (HDPE) and crosslinked polyethylene (XLPE) both resist dilute-to-moderate MCAA solutions well, which is why polyethylene storage and day tanks are commonly used for this chemistry. The honest limit is temperature and concentration: as the solution gets hotter or more concentrated, the compatibility margin narrows, and very hot or concentrated acid is better served by fluoropolymer-lined equipment such as PVDF or PTFE. Polyethylene is not attacked the way chloride-sensitive metals are, but it is not a license to ignore the conditions of service. Before specifying a tank, match your exact concentration and maximum operating temperature against the tank manufacturer's published chemical resistance chart, size fittings and gaskets in compatible materials, and provide full secondary containment given the acute toxicity and corrosivity of this acid.

Material compatibility at a glance

For ambient aqueous monochloroacetic acid solutions, polyethylene (HDPE / XLPE) and polypropylene tanks are the practical, economical choice and rate compatible (S) on the major resin resistance charts. For hot or highly concentrated acid, step up to fluoropolymer-lined equipment (PVDF / PTFE). Metals such as carbon steel and 316 stainless steel are unsuitable because chloride-driven corrosion attacks them quickly. Always confirm the exact rating for your concentration and temperature against the tank manufacturer's published chemical resistance chart before specifying.

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

• Fatal in contact with skin (H310) and fatal if inhaled (H330) - use impervious chemical-resistant gloves, full face/eye protection, and supplied-air or appropriate respiratory protection; never allow skin contact.
• Causes severe skin burns and eye damage (H314 / H318) - keep an eyewash and safety shower within immediate reach of all transfer points.
• Toxic if swallowed (H301) and causes damage to organs (H370) - prohibit eating, drinking and smoking in handling areas; decontaminate thoroughly after work.
• Very toxic to aquatic life with long lasting effects (H410) - provide full secondary containment and prevent any release to drains, soil or surface water.
• Store in tightly closed, corrosion-resistant containers (polyethylene for aqueous solutions within rated limits) away from incompatible metals; keep cool and dry.
• Have spill control, neutralization media and a trained emergency response plan in place before bringing the acid on site.

Common questions

Can I store monochloroacetic acid in a polyethylene (HDPE or XLPE) tank?

Yes for aqueous solutions at ambient temperature - polyethylene rates compatible (S) for dilute-to-moderate monochloroacetic acid on the major resin resistance charts. Confirm your specific concentration and maximum temperature against the tank maker's chemical resistance chart, and use fluoropolymer-lined equipment for hot or concentrated acid.

What materials should never contact monochloroacetic acid?

Avoid carbon steel and 316 stainless steel - chloride-driven corrosion attacks them rapidly. Natural rubber is also degraded. Use compatible polymers (PE, PP, PVDF, PTFE) and verified elastomers for wetted parts.

Why is monochloroacetic acid considered so hazardous?

It is acutely toxic by every route - fatal in skin contact (H310) and if inhaled (H330), toxic if swallowed (H301) - and it causes severe skin burns and eye damage (H314). It also causes organ damage and is very toxic to aquatic life, so it demands strict PPE, controls and containment.

Is monochloroacetic acid flammable?

It has a low flammability hazard - NFPA Flammability 1 with a flash point near 126 C (259 F). It must be preheated before it will ignite, so the dominant hazards are health and corrosivity rather than fire.