All About Anodizing & Plating

This article talks about:

  • The differences between plating and anodizing
  • Anodizing Methods
  • Application

The differences between plating and anodizing

Anodizing and plating are 2 different processes for applying a coating on metal.

  Plating Anodizing
Purpose Used to make something look good. Used to protect a surface from oxidation or corrosion.
Method Coating applied using a positive/negative application process to stick the material to the surface of the item being coated. Essentially the coating is applied on top of the product. The item is submersed in a diluted sulphuric acid bath and a negative/positive charge applied to create an oxidising barrier on the surface of the object. Essentially it is an aluminum oxide layer. Anodizing uses the product's chemical make up to apply the coating.

For example with aluminum the surface of the metal reacts with oxygen causing aluminum oxide which is harder and stronger than the product.

Durability Minimal. Purpose is to provide durability. Coating adheres at a molecular level providing a much harder and more durable finish.
Where Used Any metal, for example gold plating. Only aluminum. Generally, the higher the grade of aluminum the better the finish quality.

 

Anodizing methods

  Hard Coating (Type III) Clear Anodizing (Type II) Chromic Anodizing (Type I)
Finish Type Smooth finish. Very smooth finish using thick coating. Very smooth finish using thick coating.
Where Used Ideal for products with tight tolerance parts which receive a lot of abrasion. Good solution for exterior or interior parts exposed to weather and light abrasion. Widely used in medical field because finish allows easier sterilization. Produced using environmentally damaging chemicals so not used by Ronstan.
Finish Thickness Typically 0.001 to 0.003 inches thick. Typically 0.0002 to 0.0006 inches thick.  
Color Black only. Can be dyed to any color and is virtually fade resistant.  
Cost Most expensive method because takes longer and requires more energy to apply. Less expensive than Hard Coating. Unknown

 

Note: Sometimes Clear Anodizing is described as Architectural Anodizing. The difference is that a metallic dye is added to create a colorfast finished product. The dye uses chemicals that are damaging to the environment so it is rarely used and certainly not by Ronstan.

Application

Look at where you are planning to use the product and then identify the best anodizing method.

Are tolerances in the finished product critical? If so a thinner coating is best. When engineers design a product the buildup on the surface is part of the product. With anodizing roughly half of the coating penetrates the surface and the rest is categorised as buildup.

How much exposure to chemical is the finished product going to get? If the product is going to be exposed to weather then a thicker coating is required. If the product is going to be used in a sterile environment then a smoother finish is better.

How important is the color? Hard coating can only be supplied in black whereas clear anodizing can be any color.

For example:

Ronstan Friction Rings - black anodizing using the hard coating methodology is ideal and it will last longer than the colored options. Regarding track, traveler or safety rail systems the abrasion from roller systems is minimal so normally clear anodizing is preferred.

Ronstan staff are not experts in anodizing, but we have an understanding of what finishes will work best for what applications. We apply years of practical experience in the marine, architectural and industrial spaces to find the best solution for the application.

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