Surface treatment for sandcastings and investment castings

Surface treatment is a process applied to the surface of a material to make it better in some way, for example by making it more resistant to corrosion or wear, improving the appearance, etc.

Here is a summary about general surface treatment for castings:

1, Painting

Spray paint onto casting surface, and dry by natural or heat, painting color can be applied according to customer’s samples or color code such as RAL number

This method mainly used on carbon steel castings and iron castings.

2, Electrophoretic paint

Electrophoretic painting, also called electrophoretic deposition of paint. The process is carried out with the use of anodes and cathodes in the painting tank. There are two types of electrophoretic painting: anaphoretic and cataphoretic painting. In anaphoretic painting the profiles will be the anode, and in cataphoretic painting the profiles will be the cathode. In the electrophoretic painting process, evolution of oxygen gas will take place at the anode, and hydrogen gas will be evolved at the cathode.

It is widely used to coat many carbon steel and iron castings applied in automobile industry, metal furniture, and beverage containers.

3, Powder coating

Powder coating is a type of coating which apply dry powder to casting surface electrostatically and then cured under heat. It is usually used to create a hard and smooth finish, this method mainly used on carbon steel castings and iron castings.

4, Hot dip galvanization

This is a method to dip parts into molten zin bath, and the surface of part will be reacted with the zinc to form intermetallic layer and an outer layer of pure zinc, it’s a high anti-corrosion method, widely used on iron and steel castings in the electric transmission system and other parts used in highly corrosion environment

5, Electric galvanization

Electrical galvanizing is applied by using electricity, its zinc layer is thinner than hot dip galvanization but surface is smoother. It also can be used on carbon steel castings and iron castings. But the anti-corrosion property is not as good as hot dip galvanization.

6, Pickling and Passivation

Used to protect castings from corrosion and add a protective layer. In this process Investment castings are placed in a basket and submerged in a nitric or citric acid bath. It effectively removes free iron and foreign materials from the part’s surface, leaving the part clean and more corrosion resistant. Most of stainless steel castings can be applied in this process.

7 Electropolishing

Electropolishing removes surface imperfections and contaminants from investment castings by using a combination of chemicals and electrical current. As a result, it offers superior corrosion resistance. All the stainless teel castings can be applied in this process.

8, Mechanical Mirror polishing

It is a finish that achieved mechanically by using a progressive series of abrasives and polishing compounds to remove deep scratches on metal surface, the surface is smooth enough to provide a highly reflective like mirror. Besides the mirror finish, it also provides highly corrosion resistant. It’s widely used in stainless steel castings applied in food machine, chemical machines, furniture, etc.

If you are not sure what surface treatment should be applied for your parts, just send pics or drawings and its application, I will help to provide several solutions for you to choose.