CHEMFILM
CHEMFILM
Adding Chemfilm Processing to Your Facility
If you are thinking about adding a process line to your facility to do chemfilm, most of the articles, classes and information presented by this website are applicable to the chemfilm process, also known as chromate conversion coating or Alodine. This process is usually guided by MIL-DTL-5541 or AMS-2473, and the pre-process operations, such as the cleaner, etch, deox and desmut, are the same as those used for aluminum anodizing as per MIL-A-8625 ,AMS 2471, AMS 2472, AMS 2469, or ASTM B580.
A brief description of the steps involved in the typical Chemfilm procesragraph
Extra rinse tanks are usually required to minimize water usage & wastewater production. A desmut may be required for certain alloys and if castings are to be processed. Process times will vary based upon the specific chemistries used for each process, and will also vary based upon parts, alloys, etc. Chemfilm tank shown with air agitation to aid in mixing chemistries when making additions. Air agitation is not generally used during processing of parts.
Care should be taken in setting temperature of warm rinse tank following chemfilm because at approx.. 140 degrees F. The chromic layer will tend to dissolve.
ADDING CHEMFILM PROCESSING TO YOUR FACILITY
Here is an overview of what a typical industrial chemfilm line is likely to involve:
Note that we are assuming the parts have already been thoroughly cleaned, masked and rack-mounted prior to the chemical processing done here. Also note that the process time for the chemfilm is assuming the hex chrome variety of chemfilm and not the tri-chrome, which may take 10 minutes or more to process.
Chemfilm Classes and Types
The MIL-DTL-5541F standard calls out for Class 1A as a thicker coating to offer the maximum protection against corrosion, whether the part is then painted or unpainted. The Class 3 portion of the specification is provided for a low electrical resistance, and has a thinner coating and a lighter coating weight. Type I specifies that hex chrome be used in the chemfilm solution, and type II specifies trivalent or tri-chrome.
Chemfilm Equipment
As mentioned earlier, most of the Aluminum Anodizing Lines and Equipment in this website would also be applicable to chemfilm. In fact, since a standard Aluminum Type II Anodizing line is only just a handful of tanks shy of also allowing chemfilm, many of our customers either specify that we add chemfilm into the line when they purchase it, or they have us design the line for chemfilm and supply the empty tanks so it will be a relatively simple addition that can be made later.
Stand-Alone Chemfilm line w/ closed-loop
We have also had customers start off buying a chemfilm line to process aluminum, and then add one or more “flavors” of aluminum anodizing later.
If you are thinking of adding chemfilm processing to your facility and would like more information on what exactly that would entail, I encourage you to sign up for our free anodize classes to get a brief overview of what it might take, all from a manager’s or owners perspective. If you would like to get a quote for a chemfilm line that fits your needs, we have a handy form here:
http://anodizingequipment.com/request-for-quote/
Whether Type I or Type II, Class 1A or Class 3, adding a chemfilm line to your facility is probably not as difficult as you might think, and it offers a great payback in quality of processing, in time and in money.
by Mark Emilio
This is a stand-alone chemfilm line with closed-loop I/Xagraph