Materials may include metals, plastics, rubber, vinyl, and wood. Whatever the covering of the trailer, it must resist impact and be durable. Metal can fail by cracking, bending, shearing, or denting. Steel is known for its strength. Even all-aluminum trailers use stainless steel fasteners, along with steel axles, neck, tongue, and coupler.
Corrosion degrades metal alloys with chemical or electro-chemical reactions.
Moisture rusts steel through oxidation, although aluminum also can corrode, especially from horses' urine. An aluminum floor can deteriorate down to powder. There is help in barriers that protect metal alloys from corrosion. Flat sheet-type components like the roof and sides are usually made of galvaneal steel, which is galvanized steel that has been reheated to smooth the surface, eliminate the shiny appearance and prepare it to hold paint better. These coated steels can be scratched lightly and still resist corrosion, but welding will break down the protective chemical barrier.