Compatibility: Metals, Plastics & Elastomers

Why compatibility fails in real plants

• Temperature accelerates attack (especially with alkaline/acid cleaners).
• Concentration mistakes (wrong dilution, poor mixing, evaporation).
• Time (dwell / soaking) is longer than intended.
• Mixed chemistries (acid + hypochlorite → chlorine gas risk; cationic + anionic incompatibilities).

Step 1 — Identify what actually touches the chemical

List wetted materials for every contact point: tanks, pumps, seals, gaskets, hose liners, spray balls, valves, instruments, and heat exchangers.

Step 2 — Flag the “high risk” chemistry

• Strong alkalines (high pH / caustic): can attack aluminum, zinc, some elastomers.
• Strong acids (HCl, nitric, sulfamic): can corrode carbon steel; chloride stress corrosion risk on some stainless at elevated temperature.
• Oxidizers (hypochlorite, peroxide, peracetic): can damage certain elastomers and metals; watch concentration + temperature.
• Solvents (hydrocarbons, glycol ethers): can swell plastics/elastomers; stress cracking on some plastics.

Step 3 — Do a quick compatibility screen before a full trial

1. Coupon test (preferred): soak representative metal/plastic coupons in “worst case” conditions (max concentration, max temperature, max time).
2. Elastomer check: measure weight/size before and after (swelling/softening/tackiness).
3. Visual + mass loss: look for pitting, discoloration, haze, cracking; record any weight change.

What to request from suppliers

• SDS + TDS with pH, active components, and recommended dilution.
• Known material compatibility notes (metals, plastics, elastomers) and temperature limits.
• Any restrictions for chlorides, amines, or oxidizers in your system.

Stop conditions

• Strong odor, unexpected heat, fuming, gas release.
• Rapid discoloration, bubbling on metal, or visible cracking.
• Seal swelling or softening after short exposure.