Verzinnung

Verzinnung, or tin plating, is a metallurgical coating process in which a thin layer of tin is deposited on a metal substrate. The tin coating provides corrosion protection, improves solderability, and yields a uniform, bright surface finish. The technique is widely used on steel and iron, and can also be applied to copper or other materials with appropriate surface pretreatment.

Two main methods are used: hot-dip verzinnung, where parts are immersed in molten tin, and electroplating (electro tinning), where tin is deposited from tin salts by an electric current. Hot-dip tinning tends to produce thicker, more uniform coatings and is common for tinplate used in packaging, while electrotinning offers tighter control over thickness and appearance and is common in electronics and precision parts. Additional methods include spray tinning and immersion tin processes.

Applications include tinplate for food and beverage cans, corrosion protection for metal components, and solderable finishes for electronics connectors and printed circuit boards. Tin finishes are often chosen for their low cost, chemical inertness, and compatibility with soldering, including lead-free solders.

Quality control focuses on coating thickness, adhesion, and solderability. Thickness is typically measured by X-ray fluorescence or micrometer techniques; adhesion may be tested with standardized tape tests; solderability tests assess wetting and spreading.

Limitations and challenges include tin whisker growth under certain temperature and humidity conditions, which can pose reliability concerns in electronics. Tin coatings can also be susceptible to mechanical wear and, in some baths, environmental and handling concerns require proper waste treatment and compliance with regulations such as RoHS and REACH.