Alodine Finish
We offer complete Alodine finishing services as a one-stop shop to our clients, enabling them to capture faster turn-arounds on their precision parts and peace of mind that the high tolerance specifications for the final parts are met.
Many design engineers specify Aluminum with the assumption that it has good corrosive resistance as it does not rust like steel. While this is true for some applications, in others exposure to oils, salt water (even from human skin) or conducting electricity, the part will perform better if a coating is applied to the finished piece.
Alodine is a coating process that improves the corrosion resistance of the part without impacting the final dimensions of the part made from Aluminum. Unlike Anodizing process that has the same goal as Alodizing, an Alodine finish functions as a primer and allows the part to be painted if required. This is due to the type of process, passivation, simply applying coating applied to the part. It is important to remember this is not a cosmetic surface finish and is focused on improving part performance as seen in the table below:
| Industry | Benefits to final product | Product Example |
|---|---|---|
| Consumer and Medical Goods | Reduces corrosion and primer for paint | Aluminum Handles |
| Electrical Components | Reduces electrical conductivity loss between parts | Heat Sinks |
| Marine and Port machinery | Improved corrosion resistance to salt water | Cover plates |
| Aerospace | Improved part longevity | Flight controls and landing gear components |
When specifying this process our customers typically come from these recognized international standards.
| Organization Issuing | Standard Number |
|---|---|
| United States Department of Defense | MIL-DTL-5541 |
| International Standards Organization (ISO) | 8081 |
| Society of Automotive Engineers (SAE) | AMS 2474, AMS 2473 |
| American Society for Testing and Materials (ASTM) | B449, B921 |
At Macfab, we have studied the above standards and focused our process on meeting the MIL-DTL-5541 standard as it is the most robust and is the best foundation for meeting our customer requirements. The table below provides a quick overview of the standard.
| Type 1 (Hexavalent Chromate) | Type 2 (Hex-Free Chromate – Trivalent Chromate)1 |
|
|---|---|---|
| Class 1A | Maximum corrosion protection | Maximum corrosion protection |
| Class 3 | Less corrosion protection, improved electrical conductivity | Less corrosion protection, improved electrical conductivity |
| Process Steps | Clean Parts | Acid or Alkaline Clean |
| Rinse | Rinse | |
| Etch | Coat | |
| Rinse | Rinse | |
| Deoxidations (Deox) | 2nd Rinse if needed by coating material | |
| Rinse | ||
| Coat | ||
| Rinse | ||
| Warm Rinse | ||
| Note 1: Type 1 is tightly regulated environmental protection agencies, and Type 2 was developed as a more environmentally friendly process | ||
