2-Phosphonobutane-1,2,4-tricarboxylic acid sodium salt

2-Phosphonobutane-1,2,4-tricarboxylic acid sodium salt (CAS 40372-66-5) is the fully or partially neutralised sodium form of PBTC, a phosphonate-based chelating agent. It is supplied under trade names including Chelest PH 435 and CrestoGuard 414, and abbreviated as PBTC-4Na or PBTCNA4. No E-code designation applies to this substance.

In cooling water and boiler systems, PBTC-4Na inhibits scale formation by binding calcium and magnesium ions and disrupts crystal growth at sub-stoichiometric concentrations. In metalworking and textile processing, it functions as a sequestrant that prevents metal ion interference during formulation, and its buffering capacity helps stabilise process pH under variable conditions.

The product is supplied in aqueous solution form and is subject to REACH registration requirements within the European Economic Area. Procurement teams should confirm active content, sodium equivalence, and compliance documentation with the supplier prior to ordering.