POR 15 is an outstanding product, yet can be challenging to use. It must be applied onto clean metal surfaces free of rust; furthermore, its adhesion can vary depending on how your frame has been treated and can even peel off entirely in sheets if not done properly.
Powder coat can also be an option, although this process requires considerable prep work and an oven that many DIY shade tree mechanics don’t possess.
Cost
POR 15 and Rustoleum are both corrosion protectant coatings designed to shield metal surfaces from further deterioration, with easy application making them suitable for painting directly on top of existing rust. Both offer customizable colors and finishes for every vehicle imaginable – both can also be sprayed onto surfaces using spray guns or brushes; plus these quart-sized cans make storage a breeze!
Auto stores sell auto body filler as an economical alternative to powder coat, as they both require less preparation work than powder coating (which requires an absolutely clean and blast-free surface) as well as being much cheaper due to equipment and time requirements for application.
POR can serve as an interim fix to frame-on restorations, but won’t stand up as well to blasting and epoxy primer plus powder coat treatments – and is more costly.
Durability
Powder coating your frame requires disassembly and professional services (rather than Harbor Freight or your wife’s kitchen stove), which can be expensive and time consuming. Reassembling requires great caution in order not to interfere with its functionality (ie threaded ends of tie rods threading into bolt holes, captive nuts no longer self-adjusting etc) or risk road debris chipping the finish.
POR 15 can make this easier; simply apply it over light rust for prevention by encasing it and sealing out oxygen.
But I believe powder coat is more durable, as it withstands impacts and abrasion more effectively than paint. Therefore, for my bike frame I would opt for getting it blasted first before getting it powder coated or at the very least using high quality epoxy paint like POR 15 or VHT for optimal results.
Appearance
Powder coat has the advantage of looking great, but can be more difficult to repair after being scratched than chassis coat. I prefer chassis coat because it doesn’t chip easily and repairs much quicker if anything does happen to it; plus its less costly but takes much more time to apply than its counterpart.
POR-15 can provide a temporary fix when used to protect rusty frames during restoration projects or when blasting is impractical, yet is an effective protective layer against corrosion. Unfortunately, however, POR-15 has specific surface requirements and won’t adhere properly on fresh steel without first being heavily blasted; additionally it doesn’t last as long when applied directly on non-blasted surfaces like powder coating.
For a frame to be restored fully, I would advise blasting and epoxy primer plus top coat application.
Maintenance
POR-15 is an excellent product, but can be difficult to adhere to certain surfaces. It needs very clean, “seasoned” steel surfaces in order to adhere well, peeling off if applied directly over fresh metal, nor galvanized steel that lacks an oxide film layer. POR-15 serves best when applied over frame-on restorations when separate blasting and painting processes may not be practical or time-efficient enough.
Powder coating frames is possible, but requires more work (disassembly, dismantle/prep work to totally clean & etch the metal, spray booth setup/respirator protection/oven bake in 10″ square sections) as the powder may chip or scratch easily allowing moisture and debris to penetrate.
Paint is less costly and works just as effectively on frames, though it may chip, scratch and wear over time – with any major incident necessitating repainting of all affected areas to restore. Still better than nothing as it provides protection better than bare metal; though not quite as visually appealing!