Whether it's for protecting the part from the elements or giving it a pop of colour, choosing the right surface treatment can provide a myriad of enhancements to your workpiece. When deciding the treatment process, here are some key questions and design elements to think about before talking to your treatment house.

Surface Treatment Article.jfif

Is the Workpiece Fresh?

A fresh workpiece is a part that does not have a pre-existing coating / finish on it or it has not been used in service (i.e not exposed to contaminants like oil and grease or exposed to the air resulting in oxidation and rust). Beyond knowing this information just to charge you more, this information is important for your treatment house for this 2 main reasons:

1. Surface contaminants on the treated part might result in the finish not being consistent and at times, even causing the coating to flake off.
2. Especially for andozing, excessively dirty parts can reduce the cleaning capability of chemicals in the cleaning solution. At times it can even contaminate other treatment tanks along the line, which is costly.

Therefore, it is important to convey the state of the workpiece such that the necessary steps can be taken to prepare the part for treatment and reduce the likelihood additional hidden costs to you.

What Material is the Workpiece?

The material of the workpiece will heavily affect the surface treatment choice and the outcome of the process. For example, anodization would be more suitable for aluminum alloys because it can convert the surface layer into a hard aluminum oxide coat, but on the other hand, this is not viable for stainless steel because this oxidation process creates rust, which flakes off and weakens the material. A process like passivation or powder coating would be more suitable for stainless steel. Knowing the material can help your treatment house prepare the part more effectively and sometimes, suggest alternative finishes that achieve the same functionality at a lower cost.

What Kind of Finish is Required?

Different finishes will result in a different price. For example, in andozing aluminum:

• Type 3 Hardcoat uses a slightly different process from Type 2 (It does not just sit in the bath longer), it will require a longer lead time and cost more. However, it will result in a thicker, more wear-resistant protection.
• Matte vs Gloss finish has no difference in mechanical properties, just appearance. However, it has to be specified as the different finish is achieved through mechanical means like polishing.

Alternatively, if maintaining the conductive property of the material is important, instead of methods like anodization and powder coating, processes like electroplating and electroless plating to deposit nickel or even gold would be a better option.

Which Surface is Critical?

Most surface treatment require the treated part to be suspended in a bath, not touching the bottom of the tank, but still submerged in the solution. Therefore, there is a need to use a rack/ jig to hold the part in place. As the part needs to have a contact point with a tool to secure it, this contact point(s) will not have a great a surface finish/ coating as the rest of the part. Hence if there are any surfaces that need to be properly treated - be it for aesthetic or functional reasons - it is important to highlight it to the treatment house.

Design Elements to Think About

These pointers will serve as DFM checks to ensure that the parts will have ample coating with a low failure rate:

1. Deep Blind Holes
   • These holes could trap air bubbles and cleaning solution, resulting in the surface of the holes not being coated properly