Abstract: An alloy specifically adapted for use as a coating on a nickel-base or cobalt-base superalloys consists of in weight about 12.5% to about 20% Chromium, about 2% to about 10% Silicon, about 2% to about 8% Aluminium, optionally up to about 10% Titanium, optionally up to about 0.25% from the group comprising Yttrium and the other rare earth metals, optionally up to about 20% Iron, optionally up to about 4% Niobium, optionally up to about 4% Molybdenum, optionally up to about 5% Manganese, the Iron, Niobium, Molybdenum and Manganese being present singly or in combinations such as to produce little or no deleterious effect on the corrosion resistance, the balance comprising essentially Nickel or Cobalt or a combination of these two, and impurities.