What Finish Is Right For Your Die Cast Parts? Part 2 | Electroplating & Electroless Plating

What Finish Is Right For Your Die Cast Parts? Part 2 | Electroplating & Electroless Plating

A die casting surface finish can provide durability, protection, and an attractive appearance. Last month we detailed the most common decorative finishes used in the industry – this article will delve a bit more into two types of plating that can be applied to die castings; electro-plating or electroless plating. What is the difference between the two processes and which would work best for your application?

Electroplating
Electroplating is a process where thin layers of metal are bonded at the molecular level with another metal. An electrical current is passed by two electrode terminals through a carefully prepared electrolyte solution where a metal part has been placed for plating. The electricity changes the surface properties of the part and allows it to bond with the metals in the electrolyte solution.

What types of metals can be plated this way?
• Platinum
• Gold
• Silver
• Chromium
• Copper
• Tin
• Aluminum*
• Zinc
• Cadmium
• Nickel
• Lead

*Aluminum has a tendency to form an oxide that may prevent proper plating adhesion. It is best to apply a zinc undercoating to aluminum parts before any type of plating.

Why choose electroplating?
• Improve appearance
• Improve the abrasion and wear resistance
• Corrosion protection
• Increase lubricity
• Increase the thickness of a part

What parts are commonly electroplated? Here are a few examples:
• Tools and dies
• Aircraft components
• Machine components
• Mechanical assemblies
• Electronics and computer devices
• Enclosures, chassis, and heat sinks
• Medical diagnostic instruments
• And many more

Electroplating is capable of achieving the best cosmetic plating finish on die castings, since multiple layers of plating are applied and buffing/polishing can be performed after each layer. The main downside to electroplating is that it is very difficult to properly and evenly plate parts with complex shapes. The electroplating process also requires very clean conditions, utilizes possibly hazardous equipment, requires filtration, and typically requires multiple applications to achieve the desired look and thickness. In some instances electroless plating is the better alternative.

Electroless Plating
Electroless plating is quickly becoming one of the most widely used forms of plating today because it is more cost-effective and easier to do than electroplating. Electroless plating is used primarily as a protective and/or used to enhance electrical conductivity. In some cases, it can also be used as a decorative coating.

Electroless plating is also known as autocatalytic plating or conversion coating. Simply put, it is a process for plating a part without using an electrical current. The process for electroless plating basically involves dipping a part into a bath of plating solution where a reducing agent (like hydrated sodium hypophosphite) reacts with the ions in the part to deposit another metal alloy onto it (typically nickel).

A wide variety of metals can be plated this way, including (but not limited to):
• Aluminum
• Titanium
• Mild steels
• Stainless steel
• Hardened steel
• Copper
• Brass
• Zinc

Why choose electroless plating?
• Prevents corrosion and wear
• Adds toughness
• Resistance to abrasion
• Uniform deposits with consistent thickness
• Can be used on parts with very complex shapes

Due to the fact that electroless plating tends to create a very hard and non porous finish, this technique is very popular in industries such as oil fields or marine applications where parts are very vulnerable to wear and corrosion.

What other industries commonly use electroless plating? Here are a few examples:
• Oil and gas – barrels, pipes, pipe fittings, valves
• Automotive – gears, brake pistons, shock absorbers, cylinders
• Food service – food processing machine parts, molds
• Plastics and textiles – dies, machine parts, molds, extruders
• Aerospace – rocket parts, pumps, valves, pistons
• Chemicals – mixing blades, filer units, pumps, heat exchangers
• And so many more

In general, plating processes are the poorest at hiding underlying surface conditions and require the most surface prep operations to achieve the desired final finish. It is vital for a die cast part to have both a good internal structure and good surface finish. These are achieved through good design for both the tool and the component as well as the proper post-casting operations to achieve the optimum surface finish for the desired final plating result. Planning ahead for the finish you need can help to potentially minimize surface finish problems as well as any potential porosity issues.

With over 75 years of die casting surface finishing expertise, our engineers will evaluate your requirements to recommend the best approach to achieve the desired finish for your part. Contact A&B Die Casting today!

What Finish Is Right For Your Die Cast Parts? Part 1 | Decorative

What Finish Is Right For Your Die Cast Parts? Part 1 | Decorative

A die casting surface finish can provide durability, protection, and a decorative appearance. Over the next few months we will explore different types of finishes and how they are beneficial for different types of die cast parts.

Due to the fact that a die cast part needs to be heated during decorative finishing processes (such as plating and painting), it is vital for the die cast part to have both a good internal structure and good surface finish. These are achieved through good design for both the tool and the component. Planning ahead for the finish you need can help to potentially minimize surface finish problems as well as any potential porosity issues.

Types of decorative finish:
• Smooth and Shiny: In cases where a smooth and shiny surface is required, the density of the casting itself must be higher so that the part can be plated and buffed repeatedly. This type of finish requires the most preparation of the casting to achieve a smooth surface under the coating. Smooth and glossy finishes have the least ability to hide any surface imperfections.
• Satin and Textured: For satin finishes, brushing or media blasting can be used to achieve the desired surface finish before coating.

The 5 Most Common Decorative Finishes:
1. Painting
2. Powder Coating
3. Antiquing
4. Ceramic Coating
5. Plating

1.) Painting

Painted

Lacquers, paints, and enamels can easily be applied to die cast parts and work for both decorative and protective purposes. As with any finish, special considerations must be taken at the design stages of the part to plan for the type of painting finish you need. Precautions are taken in order to remove any oils from the cast surfaces. For best results, a conversion coating is applied after cleaning to ensure good adhesion of the coating to the die cast surface.

2.) Powder Coating

PowderCoating

Powder coating is commonly used as a decorative finish because it is able to hide minor flaws in the surface, the thickness is better controlled and more uniform, it is quite durable, very glossy, and has great color consistency and vibrancy. Powder coating yields a very hard, high anti-corrosion finish which makes it better at resisting dings and scratches. Unlike paints, powder coating reaches its final cured hardness during the baking cycle. Paints continue to cure for a period of time after baking, which may cause a delay in subsequent assembly operations. Powder coating is also quite environmentally friendly because the process produces no hazardous air pollutants or waste byproducts.

3.) Antiquing

Antiqued

In order to create an antique look, zinc castings electroplated with copper (or any other of its alloying agents), can be covered in a layer of colored components, such as copper sulfide. This casting is then ‘relieved’ – a process which entails the removal of some of the colored layers on highpoints in order to present the underlying layer of the yellowish brass or the reddish copper. The parts are then treated with lacquer in order to prevent tarnishing.

4.) Ceramic Coating

Ceramic

Ceramic coatings provide a very thin and decorative coating for die castings. Similar in thickness to anodizing, ceramic coatings can be applied to the entire part surface and in some cases even internal threads can be coated. Since the coating is very thin, any surface imperfections in the die casting will show through. Care must be taken with surface prep operations to ensure the desired final finish is achieved.

5.) Plating

Plating

Plating can be applied to die castings using either the electroless or electro-plating processes. Electroless plating is used primarily as a protective and/or used to enhance electrical conductivity. In some cases, it can be used as a decorative coating. Electro-plating is capable of achieving the best cosmetic plating finish on die castings, since multiple layers of plating are applied and buffing/polishing can be performed after each layer. In general, plating processes are the poorest at hiding underlying surface conditions and require the most surface prep operations to achieve the desired final finish.

With over 75 years of die casting surface finishing expertise, our engineers will evaluate your requirements to recommend the best design and finishing options. Contact A&B Die Casting today!

Die Casting Finish : Design Your Part For The Finish You Want

Die Casting Finish : Design Your Part For The Finish You Want

A die casting surface finish can provide durability, protection, and a decorative appearance. Due to the fact that there are so many different finish options that can potentially affect the performance of the final part it is best to discuss your specific application needs early in the design phase to ensure the proper finish for your product. The specific features of many designs also have an impact on the surface finish. For example: parting lines, ejector pins, and gates can affect the end result.

Generally, extra steps are required in die design, die construction, and casting production for the more exact¬ing finishes.

There are many different types of surface finishes that are available. Below is a list of the most commonly used surface finishes:
• Abrasive media blasting
• Burnishing
• Electropolishing
• Graining
• Industrial etching
• Vibratory finishing
• Plating
• Polishing
• Buffing
• Shot peening
• Painting
• Powder Coating

What finish you chose depends on what the part will be used for. Below is a general guide for selecting a finish:

With over 75 years of die casting surface finishing expertise, our engineers will evaluate your requirements to recommend the best design and finishing options. Contact A&B Die Casting today!