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    July 22, 2021

    What is Alodine, Chem Film, or Chromate Conversion Coating?

    A lot of different industries use Alodine coatings for a number of applications. However, there’s a lot of confusion between an Alodine, chem film, and chromate conversion coating. To help clear things up, our coatings experts put together this piece. We’ll cover all three of these styles and explain what they are. Spoiler alert: they’re all essentially the same thing.

    What Does a Chromate Conversion Coating Do?

    First off, you should know that chromate conversion coating is a general mechanical process. This form of technology adds a coating to everyday metals like:

    2 Chromate Finish Cnc

    – Aluminum

    – Tin

    – Zinc

    – Cadmium

    – Steel

    – Copper

    – Titanium

    – Silver

    – Magnesium

    The coating serves a few different functions. First off, it protects the original part from corrosion. It can also act as a primer to help adhesives and paints adhere. 

    Some people use chromate conversion coating as a decorative finish or just to keep dirty finger marks off of soft metals.

    The coating also helps to preserve the electrical conductivity in the original metal while serving these additional functions.

    How to Tell if Something Has a Chromate Conversion Coating

    The coating itself has a pretty distinct coloring. It has an iridescent green or yellow color when applied. This is a stark contrast to the otherwise gray, white, black, or silver coloring of the original metal.

    2 Metal Fabrication Chromate Finish Coating

    What is Alodine?

    If you’re using the trademarked chromate conversion coating from Henkel Surface Technology, then it’s technically called an Alodine coating. You can also call this coating a chem film or chromate conversion.

    What is Chem Film?

    Chem film is another term that’s synonymous with chromate conversion coating. It’s another general term that doesn’t refer to the trademarked process that Alodine refers to.

    How is the Coating Applied? 

    Since this is an all-purpose coating, it shouldn’t surprise you that the application can be performed in a few different styles. The coating can be applied to the base material by:

    – Brushing

    – Dipping/ immersion 

    – Spraying

    The Chromate Conversion Coating Process

    The process is pretty straightforward. Though there are some variations from one manufacturing facility to the next, they basically follow the same process.

    Step #1: Clean

    The part is first degreased. This gets rid of small impurities on the part. It also removes oxides, grease, heavy metal contaminants, and oil from the part. This helps the chromate conversion stick and creates a more even coating.

    Metal Fabrication Chromate With all of the contaminants removed, the part gets rinsed and dried.

    Step #2: Etch

    If you have sections of your part that you don’t want to coat, the piece will need to be etched. This process covers the areas in question and ensures the part gets correctly coated. 

    With the part etched, it will go through another round of rinsing and drying.

    Step #3: Deoxidize 

    Another contaminant that can ruin the chem film is oxygen. By putting the part through a deoxidization process, the oxygen, oxides, and chemicals will get removed.

    It’s really important to correctly prepare your part so the coating is perfect.

    Again, the part will be rinsed and dried to remove the deoxidizing agent. At this point, it’s ready for the processing step.

    Step #4: Apply Chem Film Coat

    Typically, the part will be fully immersed for this step. The chromate conversion coating is applied and the part will soak in the mixture for a predetermined time. This time will change from part to part and varies between methods.

    Step #5: Final Wash

    After the chem film is applied, the part will go through a series of final washes. The first is a simple rinse to remove any excess coating. The second round is a warm rinse to get a perfect surface finish.

    How Long Does an Alodine Coat Take?

    Despite the process being so specific and taking 5 steps and multiple rinses, it doesn’t take that long. Depending on the size, application, and specs, an Alodine coat will take between 10 to 30 minutes altogether.

    Industries that Use Chromate Conversion Coated Parts

    Since this technology is so universal and versatile, you’ll find a number of industries that use it.

    – Automotive Engines Of The Cargo Airplane

    – Aviation & Aerospace

    – Buildings & Architecture

    – Electronics

    – Marine

    – Medical/Dental Equipment

    – Military/Law Enforcement

    – Sporting Goods

    – Manufacturing

    You might even stumble across a box of fasteners that have been coated with chromate conversion.


    Hopefully, this cleared up the questions that you had about Alodine, chem film, and chromate conversion coatings. They are all the same process, but Alodine is a trademarked version by a massive coating company. If you want to learn more about this process or you have other manufacturing inquiries, reach out to our pros at Rapid Axis. You can reach out at any time to get a free quote and we’ll manufacture the parts that your business needs.

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