If we are ever to get ahead, if we are to gain any respite from this enormous waste of labor and natural resources, we must find ways of preventing the iron which we have obtained and fashioned into useful tools from being lost through oxidation.  Now there is only one way of keeping iron and oxygen from uniting and that is to keep them apart.  A very thin dividing wall will serve for the purpose, for instance, a film of oil.  But ordinary oil will rub off, so it is better to cover the surface with an oil-like linseed which oxidizes to a hard elastic and adhesive coating.  If with linseed oil we mix iron oxide or some other pigment we have a paint that will protect iron perfectly so long as it is unbroken.  But let the paint wear off or crack so that air can get at the iron, then rust will form and spread underneath the paint on all sides.  The same is true of the porcelain-like enamel with which our kitchen iron ware is nowadays coated.  So long as the enamel holds it is all right but once it is broken through at any point it begins to scale off and gets into our food.

Obviously it would be better for some purposes if we could coat our iron with another and less easily oxidized metal than with such dissimilar substances as paint or porcelain.  Now the nearest relative to iron is nickel, and a layer of this of any desired thickness may be easily deposited by electricity upon any surface however irregular.  Nickel takes a bright polish and keeps it well, so nickel plating has become the favorite method of protection for small objects where the expense is not prohibitive.  Copper plating is used for fine wires.  A sheet of iron dipped in melted tin comes out coated with a thin adhesive layer of the latter metal.  Such tinned plate commonly known as “tin” has become the favorite material for pans and cans.  But if the tin is scratched the iron beneath rusts more rapidly than if the tin were not there, for an electrolytic action is set up and the iron, being the negative element of the couple, suffers at the expense of the tin.

With zinc it is quite the opposite.  Zinc is negative toward iron, so when the two are in contact and exposed to the weather the zinc is oxidized first.  A zinc plating affords the protection of a Swiss Guard, it holds out as long as possible and when broken it perishes to the last atom before it lets the oxygen get at the iron.  The zinc may be applied in four different ways. (1) It may be deposited by electrolysis as in nickel plating, but the zinc coating is more apt to be porous. (2) The sheets or articles may be dipped in a bath of melted zinc.  This gives us the familiar “galvanized iron,” the most useful and when well done the most effective of rust preventives.  Besides these older methods of applying zinc there are now two new ones. (3) One is the Schoop process by which a wire of zinc or other metal is fed into an oxy-hydrogen air blast of such heat and power that it is projected as a spray of minute drops