Plating and coating

A surface finish protects a part from rust and wear and decides how it looks. The right finish depends on the metal, where the part will be used, and how long it must last, so say which one you need when you ask for a quote.

Electroplating adds a thin metal layer: zinc for rust protection, nickel and decorative chrome for looks, hard chrome for wear. Powder coating and liquid painting give a coloured protective coat. Anodising protects aluminium. Phosphating and blackodising prepare or protect steel, and hot-dip galvanising protects structures for years.

Blasting, buffing, polishing and vibratory finishing prepare the surface or give the final look. Platers and coaters usually price by area, weight or number of pieces, depending on the part.

Materials commonly used

• Mild steel and alloy steel parts
• Aluminium parts and profiles (anodising, powder coating)
• Brass and zinc die castings (nickel and chrome plating)
• Fabricated structures (galvanising, painting)

What to send with your requirement

• The finish, with colour, shade code or plating type and thickness
• The base material of the parts
• The size, weight and quantity of the parts
• Any test required, such as salt-spray hours or coating thickness
• Areas to be masked, such as threads or mating faces

What affects the cost

• The finish type and the thickness required
• Part size, shape and the number of pieces per batch
• Surface preparation: degreasing, blasting, removing old coatings
• Masking and handling of threads and fine features
• Testing and certificates

Common mistakes to avoid

• Saying only "plating" without the type and thickness
• Not mentioning threads, which may need masking or extra allowance
• Expecting the finish to hide poor machining or welding
• Not agreeing on a test such as salt-spray hours for parts that must resist rust

Frequently asked questions

Zinc plating or powder coating?

Zinc plating is thin, keeps sizes and threads close, and protects against rust. Powder coating is thicker, comes in many colours and suits covers, frames and enclosures. Many parts get both a pre-treatment and a coat.

What is salt-spray testing?

A test that measures how many hours a finish resists rust in a salt fog. If your customer asks for a number of hours, include it in your requirement.

Can threads be protected?

Yes. Threads and mating faces can be masked, or plated with a thin enough layer. Mark them on the drawing.