English version machine-translated from the Vietnamese original — under review.
Starduct proposes the use of ZAM steel sheet, with Nippon Steel's K27 coating. The differences compared with post-fabrication hot-dip galvanizing are as follows:
- Hot-dip galvanizing cannot be applied to thicknesses <1.5mm. This drives up material costs, especially for small sizes.
- The quality and thickness of the zinc coating are not uniform, making it difficult to achieve grade Z550.
- The evaporation rate of zinc is 11g/m2/year, while that of the ZAM K27 coating is 3g/m2/year. This means the corrosion-resistance service life of ZAM K27 is 3.66 times that of hot-dip galvanizing (compared with a Z550 coating). This does not yet account for the specific factors of coastal areas with high corrosivity, such as Dung Quất.
- The complex fabrication steps increase costs. Galvanizing costs are high and depend on the galvanizing contractor. There is no control over the schedule. The total cost of material + galvanizing is higher than ZAM K27.
- It is difficult to control the quality of the black steel used for hot-dip galvanizing.
