Galvanizing Flux for Metal Finishing
Specialized Galvanizing Flux formulations engineered to meet the operational and regulatory demands of Metal Finishing. Manufactured in our two Cairo facilities since 1977 and shipped to clients across MENA, Africa and Europe.
In hot-dip galvanizing, flux is the last chemical step before the zinc bath: after degreasing, acid pickling, and rinsing, the work passes through a flux bath whose double salt — zinc ammonium chloride, ZnCl₂·2NH₄Cl — keeps the steel surface active and oxide-free until it meets molten zinc. CHIMI FLUX Powder is the high-speed galvanizing grade of this double salt, used to make up and replenish flux baths; it is formulated for low fuming at the kettle and uniform zinc coats. CHIMI FLUX Solution (25-30% active content) delivers the same chemistry ready to dose, and extends to related duties: galvanizing pretreatment, oxidation prevention on prepared surfaces, welding preparation, and tin-immersion work. Choosing between powder and solution is largely operational — powder in 25 kg and 50 kg bags suits plants that manage their own bath strength, while solution in drums and IBCs simplifies handling and dosing consistency. Bath management is where quality is won: galvanizers should ask suppliers for guidance on maintaining flux density and salt ratio, controlling iron carried in from the pickle line — a major cause of dross and coating defects — and bath temperature and drying practice. Also confirm storage conditions (the powder must stay dry and moisture-free) and request the TDS and SDS for both forms.
Why Galvanizing Flux matter in Metal Finishing
About Galvanizing Flux
High-speed galvanizing flux solutions in powder and liquid forms. Ensure uniform zinc coats with low fuming and minimal ash.
About Metal Finishing
Etching solutions, passivation chemicals, cleaning agents, and surface activators for precision metal treatment.
What is galvanizing flux?
Galvanizing flux is a zinc ammonium chloride solution (ZnCl₂·2NH₄Cl) into which pickled, rinsed steel is dipped immediately before the zinc kettle. It dissolves the thin oxide film that re-forms after pickling, keeps the surface from re-oxidising while the work dries, and leaves a salt layer that lets molten zinc wet the steel so the coating forms continuously across the whole part.
Flux is supplied either as a crystalline powder that the galvanizer dissolves to make up and maintain the bath, or as a ready-to-use solution. Chemically both deliver the same double salt; the choice is about handling, storage and how the plant prefers to top up.
Double salt or triple salt — which flux ratio?
Double-salt flux (ZnCl₂·2NH₄Cl, roughly 0.8 parts ammonium chloride per part zinc chloride by weight) is the general-purpose choice for batch hot-dip galvanizing: it cleans adequately, fumes moderately and protects the dried surface well. Triple-salt flux (ZnCl₂·3NH₄Cl, about 1.2 : 1) carries more ammonium chloride for more aggressive cleaning of difficult or lightly scaled work, at the price of more fume and ash at the kettle.
The ratio is not the only variable — bath strength, temperature, pH and iron content decide how the flux actually performs — but it sets the character of the bath, and most lines settle on the double salt unless their work mix pushes them towards the more active blend.
Flux bath control: strength, temperature, pH and iron
A flux bath is a working solution, not a consumable to be dosed once. Galvanizers run it warm — commonly in the 60–80 °C band — at a controlled density, with the pH held mildly acidic (CHIMI FLUX Solution is supplied at pH 4.5–5.5) and the dissolved iron carried over from pickling kept low. Iron is the silent spoiler: it rides into the kettle on the flux film and becomes dross, so good rinsing between pickle and flux matters more than any additive.
When iron does build up, it is precipitated by oxidising it — typically with hydrogen peroxide — and adjusting the pH with ammonia so it can be filtered out, then the bath is topped back to strength with powder. Work leaving the flux is dried before dipping; wet flux flashes violently on molten zinc, and a dry, even crystal layer is what produces a clean, bright coating.
| CHIMI FLUX Powder | CHIMI FLUX Solution | |
|---|---|---|
| Form | White crystalline powder, ZnCl₂·2NH₄Cl | Clear aqueous solution, 25–30 % active, pH 4.5–5.5 |
| Make-up | Dissolved on site to build a new bath or restore strength | Ready to use — fill, top up, no dissolving step |
| Best for | Lines with their own make-up tanks; bulk consumption; long storage | Smaller lines, fast top-ups, plants without make-up capacity |
| Packaging | 25 kg and 50 kg bags | 200 L drums and 1,000 L IBCs |
| Shelf life (sealed) | 24 months, kept dry | 12 months in polyethylene |
Standards & references
- ISO 1461:2022Hot dip galvanized coatings on fabricated iron and steel articles — the specification galvanizers are measured against (coating thickness, appearance, adhesion); a sound flux stage is what lets a line meet it consistently.
- ASTM A123/A123M-24Standard specification for zinc (hot-dip galvanized) coatings on iron and steel products — the North American counterpart of ISO 1461.
- ASTM A385/A385M-22Standard practice for providing high-quality zinc coatings (hot-dip) — the design and processing practice that covers surface preparation, including pickling and fluxing, ahead of the kettle.
- ISO 14713-2:2019Zinc coatings — guidelines and recommendations for the protection against corrosion of iron and steel in structures — Part 2: hot dip galvanizing (design, venting and draining of articles to be galvanized).
Galvanizing flux — frequently asked questions
What is galvanizing flux made of?
Zinc ammonium chloride — a double salt of zinc chloride and ammonium chloride, ZnCl₂·2NH₄Cl — dissolved in water. The zinc chloride protects the pickled surface from re-oxidising and the ammonium chloride does the final cleaning as the work enters the molten zinc. Powder grades are dissolved on site; solution grades are supplied ready to use at 25–30 % active content.
What causes bare spots after galvanizing, and is the flux to blame?
Often, but not always. Bare spots appear where molten zinc could not wet the steel: oil or paint that survived degreasing, scale left by short pickling, flux that was too weak, too iron-rich or dried unevenly, or rinse water that carried one bath into the next. Check strength, pH, iron and drying on the flux first, then work backwards through pickling and degreasing.
At what temperature and pH should a flux bath run?
Warm and mildly acidic. Most batch lines hold the bath somewhere in the 60–80 °C band so the work dries quickly after dipping, and keep the pH slightly acid — the ready-to-use CHIMI FLUX Solution is supplied at pH 4.5–5.5. Exact set-points depend on line speed, drying arrangement and work mix, and are held by routine density and pH checks rather than by feel.
How is iron removed from a galvanizing flux bath?
By oxidising the dissolved ferrous iron to ferric — hydrogen peroxide is the usual agent — and raising the pH a little with ammonia so the iron drops out as a hydroxide that can be filtered or settled off. The bath is then restored to strength with powder. Keeping pickle rinses in good order is the cheaper way to slow the build-up in the first place.
Should I buy flux as a powder or a solution?
Powder if you consume a lot, have make-up tanks and want 24-month storage in bags; solution if you want to fill or top up without a dissolving step and run a smaller or faster-turnover line. Both give the same double-salt chemistry in the bath — the difference is logistics, not performance.
Does CHIMI ART manufacture galvanizing flux in Egypt?
Yes. CHIMI ART Chemical Industries makes CHIMI FLUX Powder (ZnCl₂·2NH₄Cl high-speed grade, 25 kg and 50 kg bags) and CHIMI FLUX Solution (25–30 % active, 200 L drums and 1,000 L IBCs) at its plant in 6th of October City, Giza, alongside the hydrochloric acid used for pickling and the caustic soda used in degreasing — an Egyptian manufacturer since 1977, operating under ISO 9001, ISO 14001 and ISO 45001 management systems.
Galvanizing Flux we supply to Metal Finishing
2 products in this line — every batch certified to international specifications and shipped with TDS and SDS documentation suitable for Metal Finishing compliance.
CHIMI FLUX Powder
Zinc ammonium chloride is a double-salt galvanizing flux (ZnCl₂·2NH₄Cl) supplied as a white crystalline powder for hot-dip galvanizing. CHIMI FLUX Powder is a high-speed galvanizing grade that dissolves readily in water to prepare flux baths, giving low fuming, negligible ash and thin, uniform zinc coats. Manufactured by CHIMI ART in Egypt, it is supplied in 25 kg and 50 kg bags with technical documentation for every batch.
CHIMI FLUX Solution
Zinc ammonium chloride solution is an aqueous galvanizing flux (ZnCl₂·2NH₄Cl) supplied ready to use at 25-30% active content. CHIMI FLUX Solution pre-treats steel before hot-dip galvanizing, prevents oxidation of prepared surfaces, and is also used in welding preparation and tin immersion. A clear liquid with a pH of 4.5-5.5, it is manufactured by CHIMI ART in Egypt and supplied in 200 L drums and 1000 L IBCs.
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