Sodium Gluconate — Frequently Asked Questions

Because its chelation does not depend on protonation equilibria that hydroxide disrupts. Most sequestrants lose effectiveness as pH rises, since hydroxide competes for the metal ion and precipitates it. Sodium gluconate forms stable complexes with calcium, iron and aluminium in strong caustic, which is exactly the condition inside a bottle washer or a caustic degreasing bath.

Because a caustic bottle washer would otherwise scale. Hardness in the make-up water and soil carried in on returned bottles deposit calcium and iron on the ware and on the machine, giving cloudy bottles and fouled heat exchangers. Sodium gluconate holds those ions in solution so they cannot deposit, and it does so at the high pH the wash requires.

It adsorbs onto the surface of cement grains and delays the hydration reactions that cause setting. That extends working time, which matters in hot weather and in long continuous pours where a joint would otherwise form. It also acts as a water reducer, allowing the same workability at lower water content and therefore higher final strength.

Yes, readily. It is produced by fermenting glucose and is a simple sugar acid salt, so it breaks down rapidly in the environment. That is a significant advantage over phosphonate and aminopolycarboxylate sequestrants, several of which are persistent, and it is part of why gluconate is specified in formulations designed against environmental criteria.