Aniline Storage & Tank Compatibility

Storing Aniline? Start Here

Aniline (C₆H₇N), also called aminobenzene or phenylamine, is the simplest aromatic amine: a benzene ring carrying one amino group. Freshly distilled it is a colorless oily liquid, but it darkens to yellow-brown on exposure to air and light and carries a musty, fishy odor. It is denser than water at about 8.5 lb/gal, only slightly water-soluble, and miscible with most organic solvents. Industrially it is a workhorse intermediate for methylene diphenyl diisocyanate (MDI), rubber-processing chemicals, dyes, pigments, agrochemicals, and pharmaceuticals. From a storage standpoint aniline is a mild base and a hydrogen-bonding aromatic, a combination that polyethylene tolerates only at ambient temperature and for limited duration. Its severe toxicity, methemoglobin-forming action, and carcinogenicity concern make leak-tight containment and material selection a safety priority, not just a chemical-resistance question.

Will Polyethylene (HDPE / XLPE) Hold Aniline?

The honest answer is conditional, not a clean yes. Aniline is a small, mildly basic aromatic molecule with measurable water solubility, so it does not attack polyethylene the way a strong aromatic solvent like benzene or toluene does. Published resistance charts back this up at room temperature: Braskem rates aniline at any concentration as good (++) at 20 C, King Plastic lists it as resistant, and the INEOS HDPE guide rates it satisfactory (S) at 70 F. The catch is temperature. The same INEOS guide drops aniline to unsuitable (U) at 140 F, and Braskem downgrades it at 60 C. Over time and with warmth, aniline can permeate, swell, and stress-craze polyethylene, and it will gradually discolor through the wall.

Practical guidance: HDPE or XLPE is acceptable for cool, short-term ambient handling, drum-scale transfer, and secondary containment, but it is not the right choice for long-term or warm bulk storage of aniline. For a permanent tank, specify 316 stainless steel or a fluoropolymer-lined vessel. If polyethylene must be used, keep the contents cool, plan for periodic inspection and replacement, and confirm the specific resin and conditions with the manufacturer.

Material compatibility at a glance

Aniline is a slightly water-soluble aromatic amine. Polyethylene and polypropylene are acceptable only for cool, short-term ambient handling and are not rated for warm or long-term bulk storage; published charts downgrade them to unsuitable at elevated temperature. For permanent bulk storage choose 316 stainless steel or a fluoropolymer-lined vessel, and pair with PTFE/PVDF or vetted FKM seals.

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

• Aniline is fatal if inhaled (H330), toxic by skin contact (H311), and toxic if swallowed (H301) - it is readily absorbed through intact skin, so vapor control alone is not enough.
• It is a methemoglobin former: exposure starves tissues of oxygen, causing blue-gray lips and skin (cyanosis), headache, and collapse. Treat any suspected exposure as a medical emergency.
• Classified as a suspected carcinogen and mutagen (H350/H341/H351) and a reproductive hazard (H361); minimize all contact and use a closed-transfer system where possible.
• Wear chemical-resistant gloves (butyl or fluoroelastomer, not nitrile alone for prolonged contact), splash goggles, and supplied-air or appropriate respiratory protection; provide an emergency eyewash and safety shower.
• Combustible liquid (flash point about 158 F); keep away from heat, sparks, and strong oxidizers, and bond and ground during transfer.
• Very toxic to aquatic life with long-lasting effects (H410); use bunded secondary containment and prevent any release to soil, drains, or waterways.

Common questions

Can I store aniline in a standard HDPE or XLPE poly tank?

Only with caveats. Polyethylene is rated satisfactory for aniline at room temperature and acceptable for cool, short-term handling, but published charts drop it to unsuitable at elevated temperature. For long-term or warm bulk storage, choose 316 stainless steel or a fluoropolymer-lined vessel instead.

Why is aniline only conditionally compatible with polyethylene when other amines are fully compatible?

Most water-soluble aliphatic amines are simple aqueous-leaning chemicals that polyethylene shrugs off. Aniline is different because it is also an aromatic - the benzene ring lets it slowly permeate and swell the plastic, especially when warm, which is why charts hold it back from a clean S rating.

What is the best tank material for bulk aniline storage?

316 stainless steel is the industry standard for bulk aniline; it resists this mildly basic aromatic amine and keeps the product from picking up color. Fluoropolymer (PTFE/PVDF) linings and seals are also fully resistant and are preferred for gaskets and valves.

What are the main safety hazards when handling aniline?

Aniline is fatal if inhaled, toxic by skin absorption, a methemoglobin former that causes cyanosis, and a suspected carcinogen. It is also a combustible liquid and very toxic to aquatic life. Use closed transfer, supplied-air respiratory protection, chemical-resistant gloves, and bunded secondary containment.