Powder Coating for Investment Castings

Powder Coating is a type of coating that is applied for investment castings as well as other castings. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep investment castings in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a “skin”. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of investment castings for all applications.

How Powder Coating Works

Powder coatings are based on polymer resin systems, combined with curatives, pigments, leveling agents, flow modifiers, and other additives. These ingredients are melt mixed, cooled, and ground into a uniform powder similar to baking flour. A process called electrostatic spray deposition (ESD) is typically used to achieve the application of the powder coating to investment castings. This application method uses a spray gun, which applies an electrostatic charge to the powder particles, which are then attracted to the castings. After application of the powder coating, the investment castings enter a curing oven where, with the addition of heat, the coating chemically reacts to produce long molecular chains, resulting in high cross-link density. These molecular chains are very resistant to breakdown. This type of application is the most common method of applying powders. So, we can see that powder coatings are easy to use, environmentally friendly, cost effective, and tough! Below is a picture of machined investment castings with powder coating we made:

Durability of Powder Coating

Powder coating is a high-quality finish found on thousands of investment castings. Powder coating protects the roughest, toughest castings and other metal parts. It provides a more durable finish than liquid paints can offer, while still providing an attractive finish. Powder coated products are more resistant to diminished coating quality as a result of impact, moisture, chemicals, ultraviolet light, and other extreme weather conditions. In turn, this reduces the risk of scratches, chipping, abrasions, corrosion, fading, and other wear issues.

Cost of Powder Coating for Investment Castings

Powder coating is usually cheaper than wet paint in the long run, but the upfront costs tend to be higher. Wet paint technology has been around a lot longer (powder coating was developed in the 1950s), so the equipment and materials are more widely available.

The savings with powder coating are mostly indirect, but they add up fast.

First, powder coatings have a much better utilization rate. Unlike liquid paint, powder can be collected and reused. Approximately 70% of paint is lost to overspray during application, while material loss of powder coating can be kept under 5%.

Cost is also heavily effected by safety and environmental regulation. Because it is more hazardous, wet paint requires more investment in mitigation measures and insurance premiums. Powder coating facilities can keep these costs to a minimum.

Labor costs are also lower for powder coating. It doesn’t rely on highly trained operators. Powder coating can be done well by almost anyone, or even automated.

Finally, powder coating has much lower disposal costs. Less of it needs to be disposed due to the high utilization rate, and any amount that does need to be thrown away isn’t subject to the same tight environmental controls as paint.

Advantages of Powder Coating over Other Surface Coatings

1. Powder coatings contain no solvents and release little or no amount of Volatile Organic Compounds (VOC) into the atmosphere. Thus, there is no longer a need for finishers to buy costly
pollution control equipment.
2. Powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging.
3. Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items.
4. The wide range of specialty effects are easily accomplished using powder coatings that would be imposs

So, as introduced above, there are lots of advantages of powder coating for investment castings. With powder coating, we can select any colour needed for surface coating. By comparision, cost of powder coating is relatively higher than that of wet painting, but the surface is much better. If you have a project of investment castings with such surface coating requirement, welcome to contact us!

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