A common engineering question is whether to use a type 2 or type 3 spec for anodizing. In this short article, we will discuss some common considerations that will hopefully guide you to the best approach.
The first question to ask why the part needs to be anodized in the first place? Is it simply a cosmetic consideration or do the functional properties of anodize such as corrosion resistance come into play?
If you are simply looking for dyed anodize parts for cosmetic purposes (class 2), type 2 is usually the best approach as it lends itself much better to being dyed than type 3. The reason for this is, the type 2 anodize is essentially transparent against the silver aluminum which can then be turned any color whereas type 3 appears black naturally.
For functional anodize other than just simple fingerprint resistance, type 3 is general recommended. Type 3 hardcoat is much thicker than type 2, often being triple or quadruple the thickness, and as a result, it is much less susceptible to general wear than type 2. Moreover, it has better dielectric strength, better corrosion resistance, and harder than type 2. Typically, though, type 3 anodize is more expensive than type 2 and does not dye nearly as well. The only exception to that is black dye because, as mentioned, type 3 is naturally black.
Semano offers both type 2 and type 3 anodizing and can offer you additional guidance in making your anodize decision if needed. We typically anodize according to Mil-8625 for general purpose applications or according to the different semiconductor specs for those specific applications. As such, if you are requesting a general-purpose quote for anodize, simply ask for Mil-8625 Type 3 or Type 2 and either class 1 or class 2 depending on your application.