On a wash line the detergent is usually chosen for cleaning power; from the equipment side the criterion is what it does to the surfaces and the metal parts. According to the American Galvanizers Association (AGA), galvanised steel lasts best in solutions between pH 5.5 and 12, because zinc oxide dissolves in both acid and base.
| pH | Effect on galvanised steel (AGA) |
|---|---|
| 3 to 5.5 | corrosive, where acidic cleaners fall |
| 5.5 to 12 | best performance |
| 12 to 13.5 | corrosive |
| below 3, above 13.5 | not recommended |
The pH figure alone is not enough for the decision. GEBHARDT recommends Calvatis calgonit CF 315 foam cleaner for the Isotec TBX: an alkaline product with active chlorine, it contains an inhibitor for aluminium and galvanised surfaces and gives pH 11.9 at 10 g/l, so it works at the upper edge of the window. Following the dilution instructions matters for that reason.
If descaling needs an acid, do not put the box in an acid bath; soften the water, or use the descaler on the line's own surfaces while the box is out. A chlorinated product releases toxic gas on contact with acid (SDS, EUH031), so the two are never mixed on the same surface. Write the product name, dilution and contact time into the procedure.
