Sulfamic Acid — Frequently Asked Questions

Because it contains no chloride. Chloride ions cause pitting and stress corrosion cracking in austenitic stainless steel, and a single aggressive clean can initiate cracking that fails months later. Sulfamic acid dissolves carbonate scale, rust and beerstone just as effectively while introducing no chloride at all, which is why it is mandated in many stainless and food-contact installations.

Hypochlorite. Combining the two liberates chlorine gas. Since both are common in cleaning operations, this is a genuine risk rather than a theoretical one, and cleaning sequences must ensure surfaces and equipment are thoroughly rinsed between an acid descale and any hypochlorite sanitising step.

Yes, it hydrolyses slowly in hot water to ammonium bisulfate, and the rate rises with temperature. Hot descaling baths should therefore be made up fresh rather than held, and a bath that has been hot for an extended period will have lost strength. Cold solutions are considerably more stable.

Because it is non-volatile, non-fuming, non-hygroscopic and shipped as a free-flowing crystal in sacks rather than as a corrosive liquid in bulk. There is no fume hazard when opening a container, no bunded storage requirement and no acid-resistant pumping. The solution it makes is still a genuine strong acid and requires normal acid precautions in use.