RapidDirect Alodine Finish Services

Anodizing differs from alodining based on how it works and the final part’s properties and applications.

Anodizing is an electrolytic process that involves immersing a metal electrode attached to the anode and another metal into the cathode. Passing electrical current through the circuit causes the cathode to attract positive ions from the anode, while the anode attracts O2 ions from the solution to form a passive oxide layer. In contrast, alodine aluminum treatment is a chemical conversion process.

Anodized parts offer a stronger corrosion resistance and a thick oxide layer. Alodination, conversely, produces parts with thinner coatings, offering lower protection. Anodized surfaces can be dyed in various colors, while alodined part surfaces usually have a yellow or clear chromate finish.

Alodination is important when CNC machined parts require better corrosion resistance, paint adhesion, and electrolytic conductivity with stringent dimensional tolerance requirements. Part assemblies rely on surface finishing to prevent scratches and minor damage during handling, transportation, and assembly.
Lastly, they are an important surface finish for industries that want to adhere to regulatory standards, such as aerospace, automotive, and defense.

The application process for alodine aluminum treatment involves the following:
1. Clean the part to remove contaminants such as rust and scale
2. Etch the parts that you don’t want to be coated by the alodine finish
3. Deoxide the part to removes oxides, oxygen, and related compounds
4. Immerse or spray the coating with the alodine file (the alodine finish depends on whether it is type 1 or 2) on the part. You can also apply the alodine conversion coating on the part with a brush
5. Rinse the part with deionized water and dry for a specific time

According to the USA MIL-Spec, the maximum temperature tolerance for alodine coating is 140°F. Exposure to higher temperatures can degrade the coating’s protective properties, leading to loss of corrosion resistance and hardness and reduced electrical conductivity.

Alodine coatings usually air dry quickly, often within 30 minutes at room temperature. The curing time, however, depends on factors such as workpiece size, complexity, and the alodination process.

No, the alodine finish is incompatible with stainless steel as the chromate conversion process is primarily for aluminum and its alloys. A better option is to use other methods, such as passivation or black oxide coating for stainless steel parts. The alodine finish service is the best surface finish option for stainless steel

Yes, the alodine chromate conversion Type 2 process is safe due to the use of trivalent chromium. On the other hand, Type 1 alodine aluminum treatment uses hexavalent chromium, which is unsafe and requires proper safety protocols, including personal protective equipment (PPE) and adequate ventilation.