Terne steel coatings

These alloy coatings have advantages over tin in atmospheric exposure where there is heavy pollution by oxides of sulphur. They are cathodic to steel and anodic to copper. In industrial atmospheres, however, formation of a layer of lead sulphate seals pores and produces a generally stable surface and terne-plate has been used extensively as roofing sheet, especially in the USA. It is easily and effectively painted when additional protection is required. Copper heat exchangers in gas-fired water-heaters may be coated by hot dipping in 20% tin alloy . 

Terne Plate. This is a sheet-steel product that is coated with an alloy of tin and lead. The coatings range from 50-50 mixtures of lead and tin to as low as 12% dn and 88% lead. Plate used for roofing normally is about 25% tin and 75% lead. In addition to roofing, terne plate is used in the manufacture of gasoline tanks for automotive vehicles, oil cans, and containers for solvents, resins, etc. 

After World War I, demand for lead increased considerably as motorized vehicles, automobiles and trucks had to be equipped with batteries for SLI. In addition, terne metal for gasoline tanks increased lead consumption. Terne metal is made of steel sheet, coated on both sides with a terne alloy, 80% lead and 20% tin. 

Nickel-terne-coated steel includes an electrolytic flash coating of nickel (1-1.5 g/m ) underneath a conventional lead-tin coating for enhanced corrosion resistance. Applications are similar to the conventional lead-tin alloy coatings described previously. 

Cold-rolled sheet steel electrolytically nickel flash-plated and then coated on both sides with a lead-tin alloy by a continuous hot-dip process. Corrosion resistance is superior to standard long terne. 

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