Tinapinnoitus

Tinapinnoitus, or tin plating, is a metal finishing process in which a thin layer of tin is deposited onto a metal substrate, typically steel, iron, copper, or aluminum, to provide solderability, corrosion resistance, and surface protection. There are two main approaches: electroplating and electroless plating. In electroplating, tin is deposited from a tin-containing electrolyte onto the energized workpiece, usually after cleaning and activation. Electroless tin plating uses a chemical reducing agent to deposit tin without external current, offering uniform coatings on complex geometries.

Common substrates include steel, copper, and brass; aluminum is coated after proper pretreatment to ensure adhesion. Tin coatings serve to improve solderability for electronics and provide a barrier to corrosion, helping prevent rust and diffusion of base metals. Tin is also used in the production of tinplate steel for food and beverage cans.

The process sequence typically involves cleaning, degreasing, surface activation, tin deposition, rinsing, and sometimes post-treatment such as brightening or passivation. Bath chemistries vary; traditional baths used cyanide-containing formulations in some regions, but many modern processes employ non-cyanide tin salts with buffering agents due to environmental and safety concerns.

A notable consideration in electronics is the formation of tin whiskers, slender metal projections that can grow from tin coatings under certain conditions and cause electrical short circuits. Mitigation includes alloying tin with lead or adding other elements, controlling coating thickness, and selecting appropriate finishes.

Tin plating remains a common method for improving solderability and corrosion resistance in both industrial and consumer applications, including protective canning surfaces and electrical components, though the term tinplate often refers to tin-coated steel used for packaging.