Natural passivation of Galvanized Steel produces Penta-Zinc Hydroxycarbonate (PZHC), a thermodynamically stable compound that forms spontaneously in mildly alkaline, aerated water without chemical additives.<\/p>\n\n\n\n
Its formation is highly sensitive to water chemistry and system operating conditions, and naturally ceases once a coherent protective layer is established.<\/p>\n\n\n\n
The formation and stability of the PZHC layer depend critically on a narrow envelope of water quality parameters during the initial exposure period (typically the first 4 to 12 weeks).<\/p>\n\n\n\n
Depending on the parameter, manufacturer recommendations may vary. The values presented here reflect a combination of OEM guidance, laboratory research, and field observations.<\/p>\n\n\n\n
Any passivation strategy must be adapted to the equipment and the specific operating conditions.<\/p>\n\n\n\n
| Parameter<\/th> | Recommended range<\/th><\/tr> |
|---|---|
| pH<\/td> | 7.4 \u2013 8.5<\/td><\/tr> |
| Conductivity<\/td> | 250 \u2013 2\u2019400 \u00b5S\/cm<\/td><\/tr> |
| M-Alkalinity<\/td> | 100 \u2013 500 ppm (CaCO\u2083)<\/td><\/tr> |
| Total Hardness (TH)<\/td> | > 50 ppm (Ca\u00b2\u207a \/ Mg\u00b2\u207a)<\/td><\/tr> |
| Dissolved Oxygen<\/td> | Saturated (> 6 ppm at 20 \u00b0C)<\/td><\/tr> |
| Temperature<\/td> | < 60 \u00b0C (140 \u00b0F)<\/td><\/tr> |
| Chlorides \/ Sulfates<\/td> | < 250 ppm<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n These parameters must be monitored and maintained in real time during the passivation phase.<\/p>\n\n\n\n Any deviation, such as high pH from caustic leaks or insufficient buffering from low alkalinity, can result in non-adherent Zn(OH)\u2082 or amorphous carbonates, both precursors to white rust.<\/p>\n\n\n\n A blend of co-passivating agents can be used during the passivation of galvanized cooling towers. It is compatible with natural passivation and enhances penta-zinc hydroxycarbonate (PZHC) structural development<\/p>\n\n\n\n |