Although prepared specifically for DoD applications, the standard is used for many commercial applications as well. If you are talking about “bleaching” with hot water, forget it. But something different than what you are used to is often a red flag that means it’s time to double check what happened, and that the parts actually will comply with Class 3: A certain customer has requested i. All information presented is for general reference and does not represent a professional opinion nor the policy of an author’s employer. The conversion coatings are intended for use on aluminum and aluminum alloy substrates that are not anodized.
My thinking may be, possible engineering error? We both share the same view that this could be an engineering spec. Class 3 also may have a very light gold tint as they are both processed the same with immersion time in our Alchrome II bath being the only difference. There are Class 3 compatibles out there. The situation is that you can’t comply with MIL-DTL without processing per its instructions and using the qualified products. In my opinion Alodine is applicable for type 3 coating. We run into this error quite often and the disturbing thing is that most times the customer cannot answer as to which type they actually require. The MIL-DTL specification covers chemical conversion coatings that form protective coatings by chemical reaction with aluminum and aluminum alloy; these coatings are categorized by the following types and classes.
This has led to progressively greater restrictions, imposed by national and international legislation, related to concerns over health and safety and environmental protection, on the use of these treatments.
What color is the coating supposed to be?
As far as I can ascertain, “Clear Coating” can only be applied per Class 3. It will pass salt spray requirements of the spec. It’s not possible to diagnose a finishing problem or the hazards of an operation via these pages.
They are designated as a post treatment to ion-vapor deposition IVD aluminum used on many military oer as a cadmium alternative or galvanic corrosion inhibitor. Mil-C [link is to free spec at Defense Logistics Agency, hcem. Alchrome, Alodine, and Iridite are trade names from three different companies for their lines of chromate conversion processes for aluminum.
Class 1A is less electrically conductive than class 3 and has a gold color. And one of the most common chemicals available for this class, i.
You call it chromate conversion coating; and some people classs it chem-film. Hello, I sent some parts for coating per: You can only comply with Mil-C is you use “Qualified Products” such as these; if you use “home brew” you are not in compliance with Mil-C They are used to repair anodized coatings on aluminum.
The color per se is not a problem unless you or the ultimate customer if it’s not you specified colorless. November 14, A. The situation is that you can’t comply with MIL-DTL without processing per its instructions and using the qualified products.
Note that chromate conversion coatings have been used for over 50 years as treatment to coated or as-fabricated surfaces to boost corrosion resistance and provide a good basis for the subsequent application of paint. In my opinion Alodine is applicable for type 3 coating. The MIL-DTL specification covers chemical conversion coatings that form protective coatings by chemical reaction with aluminum and aluminum alloy; these coatings are categorized by the following types and classes.
Tutorial for Newbies trying to follow this dialog: The conversion coatings are intended for use on aluminum and aluminum alloy substrates that are not anodized. Possibly an aircraft appearance item. This is a requirement due to their use on military aircraft. It has gained world wide use across many fields versus the more verbose ISO equivalent i. When it comes to aircraft fulm to 5 miles above this ground, I do not like taking chances or cutting corners.
The easiest answer is to leach the color from the side that is not painted. This page was last edited on 26 Septemberat We both share the same view that this could be an engineering spec.
Class 3 A discussion started in but continuing through Q. Indeed Robert is correct too.
Views Read Edit View history. Mooney is legally correct, but I have many clients who do a short dip in type 1a, call it type 3, and pass salt spray. I have a motto that I have kept and lived by for almost 25 years.
When coated on aluminium, do we call Mil C Class 3 “clear chromate” or “clear anodising”? The company I work for wanted to know if a class 1 can be used as a substitute for class 3? But you have to download the spec.
MIL-C E CHEMICAL CONVERSION COATINGS ON ALUMINUM
If you are talking about “bleaching” with hot water, forget it. Color wise, it may look good, but to the protective requirements of MIL-C, it will more than likely fail. Although prepared specifically for DoD applications, the standard is used for many commercial applications as well.
Retrieved from ” https: There are Class 3 compatibles out there. Type I and II conversion coatings provide corrosion protection on unpainted items, as well as improve adhesion of paint finish systems on aluminum and aluminum alloys.