Alodining (chemical conversion) is a coating method intended to provide corrosion prevention to aluminum products left unpainted, as well as to improve adhesion of painting processes.

Why would anyone want to alodine aluminum?

1. It provides good corrosion protection. It even protects when scratched. Alodined 2024 aluminum withstands salt spray 150-600 hours before forming white corrosion. Untreated 2024 corrodes in less than 24 hours.
2. It provides an excellent electrically conductive surface. This helps to provide good electrical bonding in an airframe.
3. Paint sticks to it extremely well. In some cases, it can substitute for primer.

Advantages of alodining compared to other coatings such as primer or anodizing:

1. Adds no measurable weight.
2. A more cost effective process than anodizing.
3. Does not alter the dimensions of parts (does not make holes smaller).
4. Requires essentially no cleanup after application. Encourages treatment of all small parts as they are fabricated and installed.
5. Requires no electricity or skill to apply.

Disadvantages of alodining:

1. For the best possible job, requires two large tanks capable of immersing each part. (Anodizing also requires similar large tanks.)
2. Should not be applied if the tank temperature is below 70°F (21°C).
3. The alodined surface is not as durable as anodizing or a good paint.
4. Assembled parts cannot be alodined. (Neither can they be anodized.)
5. Disposal of spent tank contents can be a problem.