During the hot-dip galvanizing technique, zinc coatings are applied to structural iron and steel components.
General Considerations
The chemical composition, surface condition and size of the steel component as well as the galvanizing specifications have a great influence on the appearance, thickness, structure, and physical/mechanical properties of the zinc coating. According to American Galvanizers Association it is the responsibility of the designer/fabricator to ensure that the product is properly designed and manufactured for hot-dip galvanizing, and the galvanizer has to ensure the compliance with the galvanizing specifications as long as the component is designed and fabricated according to the specifications. The information to be provided by the designer/manufacturer is as follows:
– The chemical composition of the component including any property that can influence the results of hot-dip galvanizing
– Identifying the surfaces that are needed to be galvanized, generally by marking the intended surface during the design or after manufacturing
– A map or guide identifying the non-level surfaces of the component
– A sample or any specification clarifying the final product requirements
– Any pre-galvanizing requirements
– Defining the acceptable specifications for galvanizing processes which are followed by centrifugation
-The desired method of inspection and quality control of the galvanized products intended by the designer/manufacturer
The following table indicates the minimum thickness/density of the galvanized components in relation to the thickness of the component:
| Component | Component Thickness, mm | Coating | |||
| Local Thickness, µm | Local Density, g/m2 | Apparent Thickness, µm | Apparent Density, g/m2 | ||
| Steel | ≥6 | 70 | 505 | 85 | 610 |
| >3 and <6 | 55 | 395 | 70 | 505 | |
| >1.5 and <3 | 45 | 325 | 55 | 395 | |
| <1.5 | 35 | 250 | 45 | 325 | |
| Cast Iron | >6 | 70 | 505 | 80 | 575 |
| <6 | 60 | 430 | 70 | 505 | |
| Threaded
(Centrifuged) |
>20 | 45 | 325 | 55 | 395 |
| >6 and <20 | 35 | 395 | 45 | 325 | |
| <6 | 20 | 145 | 25 | 180 | |
| Other including Cast Iron
(Centrifuged) |
≥3 | 45 | 325 | 55 | 395 |
| ≤3 | 35 | 250 | 45 | 325 | |
