Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers



Last updated: November 19, 2016

What Does Anodizing Mean?

Anodizing is the electrochemical process that transforms metal surfaces into a durable, decorative, anodic oxide finish with excellent anti-corrosion properties. It is a form of electrolytic passivation that is used to enhance a natural oxide layer’s thickness on metal substrates. This process is termed anodizing because the portion that is subjected to treatment builds anodic electrodes involved in an electrical circuit.

Aluminum is best suited for anodizing, but other metals, such as titanium and magnesium, also can undergo this process.


Corrosionpedia Explains Anodizing

The structure of anodic oxide arises from a substrate, usually aluminum, composed mostly of aluminum oxide, which is not used like plating or paint. Instead, the aluminum oxide is wholly incorporated with the original aluminum substrate. This prevents peeling or chipping. It is characterized by a porous, highly ordered structure that prepares the substrate for further processes like sealing and coloring.

Anodizing is achieved by submerging aluminum in an acid bath and delivering an electric current throughout the environment. A cathode is incorporated inside the anodizing tank and the aluminum in this setting serves as the anode. In this process, the oxygen ions are freed by the electrolyte to join the atoms of aluminum at the point that is anodizing. Therefore, anodizing is the process of extremely controlled oxidation or the enhancement of a natural or existing phenomenon.

Anodizing is a process that can be used for a wide range of functions:

  • It enhances wear and corrosion resistance.
  • It offers superior adhesion for glues and paint primers compared to bare metal.
  • Anodic films also provide several cosmetic effects—thin coatings enhance reflected light’s interference, while thick coatings absorb dyes.

Anodizing is also relied on to put off threaded component’s galling as well as in producing dielectric films. Particularly, anodic films are applied on surfaces to shield aluminum alloys, although the process can also be applicable for:

  • Zinc
  • Niobium
  • Magnesium
  • Titanium
  • Tantalum
  • Hafnium

Essentially, anodizing can modify the metal’s crystal structure and the texture of the substrate to achieve sealing, and this in turn leads to a high level of corrosion protection.

Related Questions
Does aluminum rust?

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