In the selection of materials for devices operating in high-temperature and high-concentration caustic soda environments, silver possesses the strongest corrosion resistance but comes with a higher price. Nickel, on the other hand, is relatively lower in cost and is commonly chosen for equipment used in the production of high-concentration caustic soda, including falling film evaporators.
The lifespan of equipment made from pure nickel is determined by the total nickel content (purity) and the levels of harmful elements such as carbon (C), sulfur (S), and phosphorus (P). Higher nickel content and lower levels of harmful elements typically indicate better quality and improved corrosion resistance in nickel materials. Therefore, the quality and corrosion resistance of nickel materials plays a crucial role in the lifespan of equipment used in the caustic soda production field.
| Grade | Ni | C | S | P | Si | Mn | Cu | Fe |
| Ni201 | 99.4 | 0.010 | 0.003 | 0.005 | 0.15 | 0.25 | 0.01 | 0.15 |
| N4 | 99.9 | 0.005 | 0.0006 | 0.001 | 0.01 | 0.01 | 0.01 | 0.01 |
From the table, it is evident that N4 nickel material has a higher nickel content and lower levels of harmful elements, particularly carbon (C), sulfur (S), and phosphorus (P), compared to Ni201 nickel material. This indicates that N4 nickel material exhibits better corrosion resistance and lower corrosion rates in alkaline environments. Additionally, the low sulfur and phosphorus content of N4 nickel material helps reduce the formation of surface microcracks during processes such as machining, plastic deformation, and heat treatment.
By utilizing military-grade N4 nickel material as the raw material for our caustic soda evaporation system, we have successfully reduced the corrosion rate and increased the lifespan by 4-6 months compared to using imported Ni201 material. This significant technological improvement allows our equipment to operate for longer durations, reducing the frequency of maintenance and component replacement.