alusvahemik

Alusvahemik is a term used in Finnish metallurgy and materials science to refer to the metal substrate or starting material on which coatings, diffusion layers, or catalytic layers are formed. The word combines alus meaning base and vahemik meaning intermediary metal, reflecting its role as the foundational material in a layered structure.

Definition and scope: Alusvahemik denotes base metals that can be pure elements or commercially used alloys. Common examples include carbon steel and stainless steel, aluminum alloys, copper, zinc, and nickel alloys. The concept is distinct from noble metals or surface-coated catalysts, which are added onto a base material rather than forming the foundation themselves.

Properties and selection: The choice of alusvahemik depends on adhesion to the intended coating or layer, mechanical strength, thermal expansion compatibility, corrosion resistance, and cost. Surface preparation is crucial and typically includes degreasing, oxide or contaminant removal, and micro-roughening to promote bonding between layers.

Applications: Base metals serve as substrates in electroplating and galvanizing, paint and polymer coatings, and diffusion coatings such as aluminizing or carburizing. They also act as supports for catalytic layers in chemical processing and as structural components in electronics, automotive, and construction industries, where the substrate influences coating thickness, diffusion behavior, and service life.

Preparation and treatment: Pre-treatment processes may involve cleaning, pickling, activation, and sometimes surface texturing. In some cases, the alusvahemik is pre-treated through annealing or minor alloying to meet specific performance requirements.

See also: base metal, substrate, electroplating, coating.