Now that we are familiar with the structures of single chain macromolecules, we are in a position to look at some of the interactions of macromolecules with other macromolecules and with smaller molecules.
Corrosion on exposed metal. Corrosion is a natural process, which converts a refined metal to a more stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment.
Corrosionpedia explains Welding Process. In the welding process, metal is melted to bridge the parts to be joined, so that on solidification of the weld metal the parts become united. Welding is often done with pressure, sometimes in conjunction with heat, to produce the weld.