This specification covers zinc master alloys which are used in hot dip galvanizing for the purpose of adjusting the concentration of certain alloying elements in the molten zinc bath. covers the chemical composition of these materials which include three master alloys of zinc-aluminum (brightener) and one master alloy of zinc-antimony. ASTM Common UNS Type A-1 90/10 Zn/Al ? High Purity Z30750 Type A-2 90/10 Zn/Al ? Low Purity Z31710 Type A-3 95/5 Zn/Al ? High Purity Z30503 Type A-4 95/5 Zn/Al ? Low Purity Z31510 Type S-1 90/10 Zn/Sb Z55710 .This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Material Data Sheet for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.