Powder coating for investment castings

Definition

Powder coating is a common way for investment castings.So what is powder coating? It is a surface treatment way that spray plastic powder on the investment castings. We could also call it electrostatic powder spraying coating. Spraying color should be consistent with the selected sample or color plate, after spraying,the color and the thickness of the surface should be well-proportioned.

Advantages of powder coating for investment castings:

*It is harmless to both human body and is also pollution-free to the environment.

*The appearance quality of coating is excellent.And the adhesion and mechanical strength is strong.

*Curing time is short when spraying.

*High wear-resistance and corrosion ability.

*Simple construction,low technical requirements for workers.

Process Theory

1.Preliminary treatment

Destination:Remove oil, dirt, rust on the surface of investment castings,and produce "phosphate layer" that could increase the spraying coating adhesion on investment casting surface.

The main process steps: oil removal, rust removal, phosphating, passivation. Investment castings after prior treatment will do not have oil, rust, dust,and generated evenly and coarse gray phosphating film on the surface.both can resist rust and increase the coating layer adhesion.

2. Electrostatic spraying

Destination:Spray powder coating evenly on the surface of investment castings.

Main process: Using the electrostatic adsorption principle, on the surface of the workpiece evenly spray a layer of powder coating.Falling powder could be used again by recycling system.

3.High temperature solidification

Destination:Heating powder coating on the surface of investment castings to certain temperature and keep some time,making it melt and flow flat, curing,thus to obtain the surface of investment castings we need.

Main process:push wear-powder coated investment castings into curing furnace,heating to a predetermined temperature (generally 185 degrees c), and heat preservation time (15 minutes).Take the castings from curing furnace and cooling down to finished investment castings.Normally,different investment castings will have different heating temperature and heat preservation time.