The adhesion of the overmolding plastic with the substrate is of course usually a relevant specifications in many applications. The issue is that the adhesion of a molten plastic with metal is intrinsically close to 0, broadly speaking. Depending on the nature of the polymer and those of the metal substrate, a specific treatment might be applied to trigger the adhesion.
Some internal studies have shown that a good adhesion between our Tecnoflon FKM and metal can be obtained during molding and curing provided a specific metal surface treatment and the use of a primer. This is well documented in this presentation.
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For applications in which the adhesion between a thermoplastic and a metal is requested, a chemical etching process is applied on the insert with the objective to get a "nano-mechanical locking". This Nano Molding Technology (NMT-one slide, NMT-thesis) developed and patented by Taisei Plas (Japan) was successfully used these last years by some of our customers for E&E applications. In order to get an overview about the current performances of this treatment, an internal study has been performed using copper, aluminum, stainless steel and magnesium. The results are presented here (under "construction")
There are alternatives like the AMALPHA process from MEC (https://www.mec-co.com/product/amalpha/en/about/feature/) or the TRI SYSTEM from Toadenka in which a nanofilm formed by a surface treatment of the metal enables a very good adhesion when overmolding.