Type I Versus Type II Anodizing

Anodizing is a process used for achieving oxidation on a metal surface through an electrochemical process. Aluminum is the most preferred metal used for anodizing purposes. There are different types of anodizing processes; type I and II are compared due to the latter’s distinct advantages over the former. Type III is the hard coating.

Any professional type II anodizing expert will be able to convince you about benefits of it over type I anodizing process.

Here is more about type I and type II anodizing processes.

What is Type I Anodizing?

In type I anodizing diluted chromic acid is used for the oxidation process. It produces a thin film of aluminum oxide over metal surfaces. The thickness of the oxidation layer can be in the range of 0.00003-0.0001 inches.

The film cannot conduct electrical current but offers other properties. It is best used on aluminum that doesn’t contain too many other elements.

It is ideal to use for aluminum components used in aviation industries. Its application is popular to use on components such as landing gear that are exposed to excessive stress. It is resistant to saltwater corrosion. The fact that it can’t conduct electrical current helps as it can be used for insulating purposes. It helps the paint stick better on metals. It also increases the strength of the adhesions used on machine parts.

What is Type II Anodizing?

Type II Anodizing is achieved using sulfuric acid in diluted form. Direct current is passed through the chemical solution, which produces the oxidation effect.

Type II anodizing conducts electricity well and offers protection from corrosion. It is also used on decorative metal items for its property to absorb colors. It is easy to use dyes on the type II oxidation surface before sealing the colors on the metal. It can help get permanent color finishes on any metal surfaces.

The thickness achieved from type II can be in the range of 0.0002-0.0012 inches.

Type II is ideal to use for industrial application where the metal needs to be hard and resistant to abrasion. It can also be used for creating matte surfaces.

Comparing Type I and Type II Anodizing – Properties and Applications

Properties and Benefits –

Type II anodizing requires less energy and time for achieving the oxidation. For type II, you need less power and heat. So, it is more cost-effective than type I. It is also easier to treat waste generated from type II processes resulting in further reduced costs. The overall process used for achieving type II anodize is less expensive than the process for type I.

Type II anodize is harder than type I. It can be used on more alloys when compared with applications of type I.

Chromic acid used in the type I process produces more toxic wastes. The waste needs to be treated with care and stored separately from other industrial wastages.

Applications –

Type II anodizing is used extensively in industries such as automotive and aerospace. It is used in computers, appliances, marine products, optical components, architectural materials, mechanical hardware, electrical items, sporting goods, hydraulic valves, and military weapons.

Type I anodizing is used mostly in aircrafts and the aerospace industry. It is also used mostly in applications where greater resistance to corrosion is needed than what you can get from type II. Point to note is that type II in no way offers inferior resistance to corrosion; type I might just be better for some applications.

Type II is an improvement over the type I anodizing process in terms of costs, properties, and applications. But both have their own distinct uses. When you need softer oxidative layers, type I is the way to go. But its use is on the decline and mostly now restricted to some components of aircrafts only. It is also sometimes used as a base for paints.

Type II offers clearly many advantages over type I anodizing. But one cannot be generally used as a substitute for another. It is better to consult with a type II anodizing expert if you wish to use it for any specific industrial use.

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