One of the main fields of application for zinc alloy products is surely the building sector. Depending on the position of the component and its visibility, various surface treatments are required to improve aesthetics and functionality.
In this article we will discuss zinc die casting finishes applied to the most common products or components in building sector:
- Chroming
- Gilding
- White zinc plating
- Painting
Zinc Die Casting Finishes for Building Sector
The use of zinc die casting components is common across many industrial sectors thanks to the exceptional properties of zinc, both in terms of accuracy of the finished product and in terms of production cost, certainly lower than many other materials.
Every sector however has different requirements concerning functional and aesthetical characteristics of the product.
When the element is not exposed to view, die casters will focus on functional product aspects, whereas if the product is visible, as in the building industry, beyond functional aspects the product must satisfy precise appearance requirements. In any case, the surface treatment covers an important role in determining product characteristics, both for resistance to wear and for aesthetics requirements.
We will now illustrate and analyze the most common Zinc die casting finishes for the building sector.
Chroming
Chroming is one of the most used die casting finishes. It is a chrome coating applied on a product or component for functional and aesthetical reasons.
For components needing both an aesthetical finish and good resistance to corrosion, an initial application of 30/40 micron of copper is required. Without this copper film, the part would be corroded by the subsequent nickel film.
The last phase is then galvanic chroming with a chrome flash that confers shine to the product.
Beyond aesthetics, this treatment confers a thicker surface film and increases the resistance to:
- Abrasion
- Dents
- Scratches
- Vapors
- Heat
- Smoke
It is necessary to bear in mind that chroming a zinc die cast component will add 60 to 70 micron to product dimensions.
Gilding
Gilding is an aesthetical process for metal surfaces. The product is immersed into a galvanic bath and exposed to electric currents which deposit material particles on the part. Exactly as in chroming, gilding requires a preventive protection by copper plating, followed by a nickel barrier and a gold flash providing the color effect and shine as required.
It might be obvious but material cost should be considered and limits the use of gilding techniques to components where the aesthetical value is essential and in high-end use.
As aforementioned, in gilding case it should equally be considered that the final dimensions of the product will increase by 60 to 70 micron.
White Zinc Plating
This treatment is often applied to components such as door hinges, hatches and handles.
The aim of white zinc plating is to improve corrosion resistance by atmospheric agents, other than product aesthetical aspects. This type of treatment will usually resist 30 hours of saline mist exposure.
Painting
Depending on the client’s requirements, alternative die casting finishes such as painting are available. In this case the treatment is not galvanic, such as for chroming, gilding or zinc plating, but electrostatic. Before painting, parts are exposed to a preliminary treatment of vibration or sand blasting to eliminate flash and sharp edges and improve adherence of the paint.
The powdered paint polymerizes on the component at a temperature of approximately 200°C.
Focus on co-design activity
It is good to point out the importance of involving the die caster during the component design phase that needs assembly, if not during the entire product design phase. The experience of a high quality supplier is essential during initial phases of the project to ensure excellent result at reasonable cost.
Often the difficulty for die casters to satisfy customer requirements is that they have to work with a design that has already been approved by a technical (hence executive) team and that they cannot suggest modifications which could vastly improve process efficiency and product quality.
A very useful service is called co-design, where the die caster helps the customer as off the very first phases of engineering the product and suggests, based on his experience, potential modifications to product and material and then engineers the mold and the process around it, resulting in optimized production within the customer’s deadline and budget.
The supplier may suggest various types of Zinc Die Casting finishing based on the process or required outcome. An experienced Die Caster will be able to identify the most appropriate treatment in order to obtain both functional and aesthetical required properties while maintaining low production costs.
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