ILZRO Classifications of Sandelin Steels
Research carried out by the University of Cardiff in Wales for ILZRO (International Lead Zinc Research Organization) project took an in-depth look at the problem of silicon reactivity and included phosphorous as a reactive element also. The researchers varied the weight percentage of silicon and phosphorous and then assessed the reactivity of the steel at different galvanizing temperatures. This work led to a table of reactivity classifications for silicon and phosphorous content.
| Class | Silicon Weight (%) | Phosphorous Weight (%) |
Steel Reactivity | Coating Appearance |
|---|---|---|---|---|
| 1. Normal / Hypo-Sandelin | 0.000 - 0.035 | 0.000 - 0.025 | Generally Normal But Occasionally Low |
Few Defects |
| 2. Semi-Sandelin | 0.000 - 0.040 | 0.025 - 0.035 | Normal | Localized Defects Due to Outbursts of Zeta Alloy |
| 3. Non-Classical Sandelin | 0.000 - 0.040 | > 0.035 | High, Especially with High Phosphorous Content |
Pronounced Surface Defects (e.g. 'Tree Bark'): High Tendency to Flake |
| 4a. Sandelin (Low Phosphorous) | 0.040 - 0.135 | < 0.010 | Moderate, Increasing With Silicon Content |
May Appear Normal With Few Defects |
| 4b. Sandelin (High Phosphorous) | 0.040 - 0.135 | > 0.010 | High | Generally Few Defects |
| 5a. Hyper-Sandelin (Low Phosphorous) | 0.135 - 0.350 | < 0.030 | High, But Generally Thinner Coatings Than On Class 5b |
May Appear Normal With Few Defects |
| 5b. Hyper Sandelin (High Phosphorous) | 0.135 - 0.350 | > 0.030 | High | Tendency to Flake, Especially With High Phosphorous Content |
| 6. Extreme Hyper-Sandelin | > 0.350 | > 0.000 | High, & Increasing With Silicon Content | Tendency to Flake, Increasing With Phosphorous Content |
For more information on steel selection and the impact of silicon and phosphorous on the HDG coating structure, see the following related articles:
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