Surface finishing options

Does your part require a surface coating, but are you uncertain which option is best? Dynacast offers a diverse range of approximately thirty coatings, from chrome to electroless nickel and beyond. This comprehensive guide explores several key coating types, their characteristics and suitable applications.

While this blog covers many options, Dynacast continually introduces new surface coating solutions based on customer requirements. If you require a coating not listed here, please contact our team.

For detailed information on specific surface finishing options, consult one of our design engineers.

Chrome vs. chromate

Before considering specific coatings, it is essential to differentiate between chrome and chromate. Chrome, derived from chromium, is an electroplated finish often associated with a shiny, metallic appearance, as seen on vehicles. Chromate, conversely, is a corrosion-resistant conversion finish rather than an additive coating. Dynacast provides numerous options for both chrome and chromate finishes.

Chrome plating

Bright chrome: This mirror-like finish is familiar from vehicles, toys and furniture. It offers corrosion protection, good wear life and aesthetic appeal.

Satin chrome: Similar to bright chrome but with a duller finish. Both finishes involve rack plating with layers of copper, nickel and chrome.

Chromate with zinc

Zinc coatings are soft, decorative and corrosion-resistant, protecting the base metal through sacrificial corrosion. Chromate application enhances corrosion protection.

• Clear chromate with zinc: Exhibits a slightly iridescent blue hue.
• Yellow chromate with zinc: Imparts a yellow colour to the finished part.
• Black chromate with zinc: Provides a black finish.

Chromate without zinc

Black chromate without zinc is an inexpensive type of chromate. It is typically used for parts that do not require a high level of corrosion resistance. The coating is applied directly to a zinc die cast part. Yellow chromate parts are chemically milled and then chromated. This gives the part a dull finish. Both of these coating options are very thin and add no measurable thickness to the overall coating.

Additional chromates

• Olive drab chromate: Features a dark green finish and withstands 150 hours to white corrosion.
• Trivalent chromate: Offers similar properties to traditional chromate without containing hexavalent chromium. Environmentally friendly, with a bright blue colour, and exceeds automotive specifications.

Nickel plating

Nickel plating, characterised by a yellowish-white colour and hard, reflective finish, excels in wear resistance, solderability and dimensional repeatability. Typically applied over copper on die castings, it also serves as a base layer for chrome plating.

• Bright nickel: The most common type, but use caution with cold forming due to potential loss of ductility.
• Watt's nickel: Offers a satin finish and improved ductility, suitable for components requiring cold forming.

Electroless nickel

Unlike electroplating, electroless nickel deposition does not require an electric current. This process produces exceptionally uniform coating thickness. It is widely used for its corrosion, wear and abrasion resistance, along with ductility, lubricity, solderability and hardness.

• Low, mid and high phosphorus: Varying phosphorus content influences properties.
• Black and dark blue electroless nickel: Primarily for decorative purposes.

Tin plating

Tin plating is ideal for components undergoing soldering during assembly. It offers excellent ductility, high solderability and good surface coverage.

• Matte tin: Typically exhibits better solderability than bright tin.
• Bright tin: More commonly specified due to its superior appearance.

Cobalt-tin

Resembling chrome in appearance and application, cobalt-tin involves copper/nickel plating followed by a cobalt-tin flash for a chrome-like finish. It is known for its hardness and durability.

Silver plating

Silver is valued for its low cost, despite its susceptibility to sulphur tarnishing. It is primarily selected for decorative, electrical conductivity or thermal conductivity purposes. It offers high electrical and thermal conductivity, solderability, malleability and ductility.

Gold plating

Frequently used in consumer electronics due to its low contact resistance, solderability and wire bonding capabilities. Alloying with cobalt enhances hardness and wear characteristics. Gold plating is available in four types: pure gold, hard gold, electroless gold and immersion gold. Refer to the surface finishes page for details.

Cadmium plating

Offers exceptional corrosion protection, approximately double that of zinc. Commonly used in aerospace, marine and saltwater environments.

Brass plating

Primarily used for decorative purposes, brass plating can be applied in bright or satin finishes and oxidised for an antique appearance. A lacquer topcoat can enhance coating longevity.

Chem film

Chem film, also known as a conversion coating, is specifically designed for aluminium die castings. The coating's colour can range from dark golden brown to light yellow, depending on various factors. Importantly, chem film does not alter the part's dimensions. There are two primary types of chem film: Class 1A and Class III, which are detailed on Dynacast's surface finishing page.

Black e-coat

Black e-coat is a paint coating electrically applied to enhance a part's appearance and protect its surface.

Anodising

Anodising creates a non-conductive, protective coating that seals the part. Commonly used types include clear and black anodising. The final colour is influenced by the die casting alloy, with aluminium exhibiting minimal colour change. Anodising allows for various colour dyeing options, with black, blue and red being the most popular. Two classes exist: Class 1, the natural colour without dye, and Class 2, dyed to a specified colour.

Polyurethane paint

Renowned for its exceptional durability, polyurethane paint is often recommended for outdoor or exposed parts. It can be applied in smooth or textured finishes and typically air-dries, although baking accelerates the process.

Powder coating

Powder coating surpasses standard wet paints in terms of thickness uniformity and colour consistency. The coating process involves curing at elevated temperatures, resulting in exceptionally tough finishes. Beyond its high hardness, powder coating is visually appealing, effectively conceals minor surface flaws and delivers a durable, high-gloss appearance. Additionally, it is environmentally friendly, posing no air quality or hazardous waste concerns.

Black oxide

Black oxide provides a protective, corrosion-resistant finish. While commonly associated with firearms, it also finds applications in spark plugs, furniture brackets and mower blades. The black finish is chip-resistant and acts as an absorbent for oils or wax. Its economic nature, coupled with its ability to extend a part's service life and performance, makes black oxide a valuable coating option.