Can You Store Sodium Hydroxide in a Poly Tank?
Yes, keep it warm and avoid drilled fittings.
By James Riggins, Lead Engineer, Liberty Chemical & Equipment Supply, Inc.
Yes. Sodium hydroxide is commonly stored in polyethylene, and Poly Processing specifies XLPE with a molded outlet flange. The two real risks are crystallization, because the solution goes solid if the tank is not kept warm enough, and leaks, because caustic finds leak paths at drilled sidewall fittings.
Sodium hydroxide (caustic soda): tank spec points
| Point | What the manufacturer documents | Source |
|---|---|---|
| Resin | XLPE. Assmann also cites better stress-crack performance from cross-linked resin in sodium hydroxide service. | Rule: crystallization and containment |
| Outlet | A molded (not inserted) outlet flange avoids the sidewall drilling that mechanical fittings need, which matters for a chemical that finds leak paths. | Rule: crystallization and containment |
| Temperature | The solution crystallizes and goes solid below a specific temperature, so keep the tank above it. | Rule: crystallization and containment |
| Hazard | Caustic is slippery, extremely corrosive to tissue and highly toxic if ingested, so plan containment and spill response. | Rule: crystallization and containment |
Frequently Asked Questions
Why does a caustic tank freeze solid?
Sodium hydroxide crystallizes and goes solid if it is not kept above a specific temperature for its strength. This is a storage risk in cold weather and outdoors.
What outlet should a caustic tank have?
A molded outlet flange instead of a drilled sidewall fitting. Caustic finds leak paths, and drilled holes add maintenance points.
Does caustic cause stress cracking in polyethylene?
Assmann identifies cross-linked resin as improving stress-crack performance in sodium hydroxide service, which is why XLPE is the usual choice.
Related
Other chemicals
Tanks by material and shape:HDPE / polyethylene tanks · Polypropylene tanks · FRP (fiberglass) tanks · Vertical tanks · Cone bottom tanks · Flat bottom tanks · Horizontal tanks · Rectangular tanks · Double-wall tanks
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Reviewed by James Riggins, 30+ years specifying water and chemical process equipment · Updated