Cement-based paints, silicone treatments, and linseed oil were discussed in the first portion of this article on protective coatings. This article will discuss three other types of protective coatings. Bituminous coatings can be produced of either asphalt or tar. The coatings can vary from thin applications to built-up coatings consisting of membranes of asphaltic-impregnated felt with moppings of pitch or asphalt. In exposed areas, bituminous coatings are temperature sensitive and this is one of the problems with the material. At higher temperatures, they flow somewhat readily and are liable to be tracked by vehicles or become rutted by the weight of the vehicular traffic. At lower temperatures, their ductility is reduced to such an extent that they crack easily. Another disadvantage of the bituminous coatings is their deterioration by oxidation and by ultraviolet light when exposed to the actions of air and sunlight. These changes can cause the film to become brittle and consequently crack. For interior slabs where a hard surface is required to resist traffic, a popular and relatively inexpensive method of increasing the surface hardness of the concrete is by the use of so called liquid floor hardeners. In this application the surface of the concrete is hardened by the chemical reaction between the magnesium fluosilicate in the hardener and the calcium hydroxide and calcium carbonate in the concrete. It should be remembered in using treatments of this kind that it is only possible to effectively harden concrete which is reasonable good in the first place. A very weak and dusting surface cannot be brought to the hardness of a good quality concrete floor which as not been treated. Metallic compounds for floors usually consist of iron aggregate with a compatible water-reducing agent, free of oil, grease, rust, and other harmful impurities and properly graded for maximum efficiency and results. Metallic floors form an excellent wearing surface for areas of heavy traffic and are extremely strong and highly resistant to impact. Since they contain iron they may rust slightly.