All five ASTM B6 zinc grades with their zinc minimum and their lead, cadmium, iron and tin maximums, mapped to EN 1179 and ISO 752 names. What to write on the order so the chemistry is unambiguous.
ASTM B6 is the reference standard for primary zinc ingot in international trade. It defines five grades, and for each one it fixes both the zinc minimum and a separate ceiling for every impurity. Writing "SHG zinc ingot" on a purchase order is not enough, because the same three letters point to different chemistry in different standards. This post gives the full ASTM B6 table and maps it to EN 1179 and ISO 752.
ASTM B6 covers primary zinc, that is metal won from ore. Secondary zinc, remelted from scrap or from galvanizing dross, is outside the standard and cannot be sold under these grade names. The standard defines chemistry only: mould weight, dimensions and packing are left to the commercial agreement.
| Zinc (min) | ASTM B6 | EN 1179 | ISO 752 | Typical use |
|---|---|---|---|---|
| 99.995% | LME Grade | Z1 | ZN-1 | Galvanizing, die-casting alloy, zinc oxide |
| 99.99% | Special High Grade | Z2 | ZN-2 | Galvanizing, alloy production |
| 99.95% | High Grade | Z3 | ZN-3 | Brass, general alloying |
| 99.5% | Intermediate | Z4 | ZN-4 | Lower-specification alloying |
| 98.5% | Prime Western | Z5 | ZN-5 | Limited industrial use |
The zinc minimum alone does not define the grade. Two ingots can carry the same zinc percentage with a different impurity distribution, and in the melt that difference is what shows up. Iron drives dross in a galvanizing kettle, lead drives specification compliance in brass, and tin and cadmium drive grain-boundary corrosion in zinc die-castings.
| Element (max) | LME Grade | Special High Grade | High Grade |
|---|---|---|---|
| Lead (Pb) | 0.003% | 0.003% | 0.03% |
| Cadmium (Cd) | 0.003% | 0.003% | 0.01% |
| Iron (Fe) | 0.002% | 0.003% | 0.02% |
| Tin (Sn) | 0.001% | 0.001% | 0.001% |
| Copper (Cu) | 0.001% | 0.002% | 0.002% |
| Aluminum (Al) | 0.001% | 0.001% | — |
The step change sits on the High Grade row: the lead ceiling loosens tenfold and so does iron. If you run a continuous galvanizing line or produce low-lead brass, that row is not for you.
