This book offers an in-depth scientific review of the effects of hydrogen on aluminium and aluminium alloys. Industrial processes yielding aluminium products are normally conducted in environments containing sources of hydrogen from which they absorb the gas as a contaminant. These products are vulnerable to damage by the hydrogen they absorb because the solubility of the gas in the solid metal is low. The damage is due to internal or subsurface defects that are essentially extended hydrogen traps of one form or another, some inherited from unsoundness and inclusions in castings and ingots and others introduced during subsequent thermal and mechanical treatment of the solid metal in course of fabrication to semi-finished products. Characteristic examples of the damage are blistering or other surface blemishes on heat-treated rolled sheet and extrusions, discontinuities across load-bearing sections, inadequate surface finish for anodic quality products and failure to contain fluids in near-net shape castings. These effects once took a heavy economic toll in lost quality and reduced yield.Moreover the recovery of useful metal was unpredictable, incurring costs for make up charges and unwanted excesses. The author is an acknowledged expert on the subject and has worked both in academia and for several of the largest aluminium producers.