Ensuring optimum adhesion and durability of primers and paints.

[juicegoose]

I've been reading over posts for the last couple days and have learned a great deal on painting plastics. Let me start by saying that although I do enjoy building models from time to time this question is actually in regard to a different medium. 

I build fishing rods and part of the process is using a graphite plastic reel seat. I've taken on the task of painting these seat similar to a company that offers the service. I'm wanting to make sure I can get the best adhesion to the plastic as possible and also increase durability as these will see abuse. Not so much in the way of flex but just generally hitting stuff.

Here is my current process and could you seasoned vets please let me know if there is an area that I could do differently to improve adhesion/resistance to chipping. 

1. Sand reel seat with 220 grit sandpaper to remove any coatings and make a good surface for primer

2. Wash with hot soapy water and allow to dry.

3. Apply mist coat of Duplicolor automotive sandable primer. Let set for a couple minutes then a 2 additional cover coats of primer.

4. Let dry for 30-45 minutes and wet sand with 600 grit

5. Wash and let dry

6. Apply light coat of primer to cover any areas where sanding through primer occured(need even color for the HOK Kandy base coat colors I use)

7. After 30-45 minutes I apply 3 medium wet coats of House of Kolor Kandy Base Coat paints. 

8. Let dry for 30-45 minutes

9. Spray 1 tack coat and 2 more wet coats of House of Kolor Show Klear. 

What you guys think? areas to improve? could I use say 120 grit for initial primer grab?

 

[Ace-Garageguy]

Over the years I've had occasion to paint a lot of full-scale stuff, ranging from high-end cars and aircraft to presentation product-design prototypes. Your procedure sounds like it's spot on...though I usually go with 180 grit for my pre-primer sanding.

A cleaning with 70% isopropyl alcohol both before you sand and after is good insurance. (Cleaning before sanding removes any contaminants that can possibly get 'sanded' into the surface if not removed.)

If you can, I'd try to let your primer dry at least overnight before color coating too. Wipe it again with iso just prior to paint. I've had fisheyes come up out of nowhere when I thought there was no possibility of contamination...but not since I've started the iso cleaning before paint too.

If you want even better adhesion and chip-resistance, about all you can do is to go to epoxy primers and paints.

Edited May 20, 2016 by Ace-Garageguy

[Harry P.]

I agree with Bill... epoxy paints would be the way I'd go. Nothing's tougher.

[juicegoose]

Thanks for the great info Bill. I will keep a bottle of Iso close by now. So you would use that over hot soapy water?  Also I agree on letting the primer set overnight. I was concerned over the can stating to coat with paint within an hour or after 24 hours. What would happen if it wasn't exactly 24 hours. Would the epoxy paint lay down thick? My concern is the threading. Although the reel seat nut has a lot of play my concern would ultimately be gumming up the threads.

I'm interested in the kd3000 series epoxy primers from HOK. Do you guys think it would be a vast inprovement in durability? 

 

Thanks again truly.

Edited May 20, 2016 by juicegoose