Powder Coat Part 3: Surface Preparation
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There are a number of different ways to approach surface preparation and steps “people” say you must follow. Some of those steps can get quite elaborate. At my level of operation, they are not all practical or possible to accomplish, and for that matter, needed.
Possible surface preparation methods include pressure washing, soaking in a cleaner, scrubbing, grinding, sanding, wire brushing, and cleaning with acetone.
All of this will depend on what you are cleaning, both the type of material you are cleaning (aluminum, cast iron, etc.) and what is being cleaned off the material (grease, rust, paint, etc.).
I believe you will have to bite the bullet and be prepared to sand blast. It will pretty much work on anything, and has the added benefit of profiling the surface (giving the surface the same uniformed texture) and give the power something to bite a hold of.
Here are some precautions you need to take when sand blasting.
> You can warp thin pieces of metal from the surface heat created by friction when sand blasting. Reducing the pressure when cleaning thin pieces helps.
> Never use play sand as a blasting media. I use Black Beauty in a medium grit. It is low in dusting, low in free silica, and chemically inert. There are other products out there that have the same properties. Black Diamond is one of them. 
Using play sand for sandblasting is dangerous and not advisable as the sand contains silica quartz, which, when inhaled, can cause silicosis
A simple respirator is not enough to prevent this.
> You want to keep your sand a clean as possible, scrape as much grease, tar, and other gunk off the piece before you put them into the blasting booth.
> Use a blasting cabinet. TP Tools and Equipment http://www.tptools.com/ has several different size booths. A booth is nothing but a sealed cabinet with a viewing port, a blast gun, ventilation system, and a light source. This is an important piece of equipment in the process of powder coating. I started with a small cabinet from (shudder) Harbor Freight and quickly upgraded to a larger cabinet.