Where the
world gathers for metal finishing
Q&As since 1989


-----

Adhesion - Chem film vs Type I anodize

We are providing parts to a customer that requires a surface prepared for priming.

Which will provide the best adhesion:

Chem film
Type I or II anodize
FPL etch

Thanks.

Greg Zeronian
M.C. Gill Corporation - El Monte, Calif., USA
2006

---

2006

Greg,

There is only one way to tell and that is to do samples of each preparation method, paint them and then test them for adhesion.

I would suspect that the order would possibly be Type I anodise, Type II anodise, FPL etch and then chem film.

The choice of pre-treatment will also depend on final application. FPL etch gives good adhesion in the short term, but it offers no corrosion protection, so after time the adhesion will degrade quite badly.

Similarly chem film when fresh is fairly soft and easily damaged, so adhesion improves with time.

You can improve adhesion of the top coat by using a good high adhesion paint primer.

Without further details of the paint scheme or the application of the part in service I can't be more specific than that.

Brian Terry
Aerospace - Yeovil, Somerset, UK