During sheet steel production, the steel surface is usually coated with metal alloy for corrosion protection. This can be done by passing the steel through a bath of the molten metal coating, and controlling thickness with a pair of air knives on either side of the ascending steel strip. Surface quality problem, have arisen with recent developments in production. The process was considered at the 2009 Mathematics-and-Statistics-in-Industry Study Group in Wollongong (MIS09) and in subsequent investigations. Previous analyses are extended by the addition of shear terms and by exploring the effect of increased air-jet speeds. A first-order partial differential equation governs the system. This may be used to determine the steady-state coating shape and to study the evolution of any defects that may form