Zinc Ingots: SHG 99.995 and IS 209 Grades

SHG stands for Special High Grade. In Indian trade it means zinc of 99.995 percent minimum purity, the grade added to IS 209 by its second amendment in 2010. The same figure is the London Metal Exchange delivery grade, and BS EN 1179 grade Z1, ISO 752 ZN-1 and the LME grade in ASTM B6 all set 99.995 percent zinc with essentially the same impurity limits.

In SHG zinc, total impurities may not exceed 0.005 percent. Lead and cadmium are each held to 0.003 percent, iron to 0.002, and tin, copper and aluminium to 0.001. SHG is the most commonly traded grade, so it is usually what a buyer is offered unless the enquiry asks for something else.

IS 209 originally listed two grades, Zn 99.99 and Zn 99.95, and the 2010 amendment added Zn 99.995. The difference lies almost entirely in lead, cadmium and iron. Zn 99.95 allows up to 0.025 percent lead, about eight times the SHG limit.

For zinc die-casting alloys such as the Zamak family, SHG is a must. Lead, cadmium and tin above tiny levels cause intergranular corrosion in zinc-aluminium alloys, which makes castings swell, crack and crumble over time. Alloy makers therefore buy SHG and add only the aluminium, copper and magnesium they want.

For hot-dip galvanising, the bath chemistry is managed by the galvaniser, and many use SHG as the base and add controlled amounts of other elements themselves. Brass mills and zinc oxide makers often accept a lower grade, depending on their own product specification.

In a galvanising kettle, molten zinc at around 440 to 460 °C reacts with clean steel to form zinc-iron alloy layers topped with almost pure zinc. Iron picked up from the work and kettle forms dross at the bottom, and lead or bismuth is sometimes added deliberately to improve drainage. Starting from a known, clean zinc makes these additions predictable. Fabricators in Karnataka who galvanise structures or pipes in-house often buy zinc in small lots, so tell us your kettle size and we will quote accordingly.

Brass is copper with zinc, from about 30 percent zinc in 70/30 cartridge brass to about 40 percent in 60/40 free-cutting brass. Brass foundries and remelters add zinc ingot to correct composition, since zinc boils off readily from molten brass. Our brass range covers the finished rods, sheets and tubes. Zinc is also a minor element in gunmetal.

Zinc ingots are flat slabs, usually with notches or a lip so they can be stacked and strapped into bundles. Individual ingot weights vary with the producer, so if your kettle or crucible needs a particular size, mention it at enquiry. Store them dry and under cover. Zinc does not rust, but a damp ingot develops white corrosion product, sometimes called white rust, and any moisture must be driven off before the ingot goes into a molten bath. Each ingot is marked with its lot number, grade and producer, which ties it back to the certificate.

Zinc ingots are for melting. Platers who need zinc anodes for zinc electroplating and fabricators who need zinc sheet are better served by the zinc products page. Every ingot lot from Jubilant Impex can be supplied with a test certificate through a Government-recognised test house, showing zinc content and the impurity values against IS 209.