Passivation solution

Category Raw Materials Published 2026-03-31 Source www.boerfibre.com

Abstract

A passivation solution improves the corrosion resistance of workpieces and extends service life. The third-generation passivation solution, beyond the trivalent chromium and acid of the second generation, adds silicon — usually wet colloidal silica — which: (1) forms a gel with stronger adhesion on the galvanised sheet after drying; (2) traps hexavalent chromium in the gel to slow its loss and extend self-healing time; (3) provides auxiliary barrier corrosion protection; (4) improves paintability by acting as a polar-particle medium that bonds with the top coat; and (5) improves finger-print resistance by giving a more uniform pale-yellow film.

The article defines a passivation solution as a product that makes a metal surface passive, forming a surface state that blocks oxidation, with main components such as chromic, nitric and sulfuric acids and metal salts. It also gives a reference trivalent-chromium passivation formula (e.g. chromium nitrate 10–18%, sodium nitrate 10–20%, sodium chloride 5–10%, water balance), noting that hexavalent chromium is highly toxic/carcinogenic and increasingly restricted by environmental rules.

Key facts

  • Purpose: raise corrosion resistance, extend service life of workpieces
  • Third-generation addition: colloidal silica (wet)
  • Five silica roles: adhesion; slow Cr(VI) loss / self-healing; barrier; paintability; finger-print resistance
  • Main components: chromic, nitric, sulfuric acids and metal salts
  • Trivalent-chromium reference formula: chromium nitrate 10–18%; sodium nitrate 10–20%; NaCl 5–10%; water balance (mass %)
  • Note: Cr(VI) is toxic/carcinogenic and increasingly restricted by environmental rules

The original article is in Chinese; see the Chinese version for the full text. This page provides the English title, abstract and key facts only — translated and compiled from the original, without full verbatim translation.