What are the positive and negative roles of diffusion?

Diffusion is a phenomenon in which the interpenetration of molecules of interacting substances occurs.

Positive role: obtaining various alloys, mixtures, compositions; welding; mixing paint (coloring); the use of perfumes, aerosols; home canning; dyeing and impregnation of fabrics, treatment of hard surfaces with special compounds against rust, mold, decay; covering one metal with a thin layer of another; metabolic processes in the body – digestion, respiration, etc.

Negative role: pollution of air, rivers, seas, soil; the metabolism in the body also occurs due to this phenomenon, so the infection of different parts proceeds very quickly; odors quickly absorbed into clothing.