You have lots of options for finishing a metal project. Most often you want to prevent rust and protect it against scratches. The best bang for your buck is typically powder coating.
Alternatives to powder coat and why not to use them
Spray paint – very inexpensive but not durable thus not protective. Spray paints require a shelf life, and thus have preservatives in them that cause the paint to cure slowly. Spray paints do not reach their full hardness for one year!
Anodize – works only on aluminum, very hard very durable, will take up color nicely. Expensive and caustic chemicals required for home anodizing.
Blue – controlled rusting for steels, moderately hard and durable. I’ve never blued anything myself but I imagine the chemicals are quite caustic. Produces a beautiful finish though, and I probably wouldn’t want to strip the blue from my gun to powder coat it.
Chrome Plate – Nice finish, but expensive to do yourself. Only works on steel unless you plate on intermediate coats.
Things you should powder coat
Knives – My KaBar came factory powder coated, once I’ve worn it away from use, I can redo it if I want. Just make sure to take the leather or rubber part off prior to starting because it’ll go away in the oven. You’ll have to sharpen through the powder that is on the edge, but this shouldn’t be a problem.
Axes, hammers, screwdrivers, prybars, shovels – Tools are great when powder coated, they are now protected against rust. If you use a hard epoxy powder they won’t scratch or mar when they’re used. Just don’t leave them in the sun for days.
Ammo boxes – they look slick in colors besides OD Green, but you have to strip the paint off first.
Car parts – High Temp powders work on just about everything in your vehicle that gets hot, and they protect from rust. Or you could make those old wheels look new with a nice metallic coating. Remove rubber first!
How powder coating works
A powder coating system works by charging particles of powder paint with 50 to 100 kV of static electricity. These positively charged particles are attracted to the grounded metal part that they’re blown towards and they stick. The powder then must be baked on using an oven or a heat lamp. Cure times are typically 20 minutes. Once the part has cooled, the surface has reached its full hardness.
Different kinds of powders
TGIC/Polyester – These coatings are excellent for most applications. Polyester coatings produce excellent gloss finishes available in lots of colors. They’re resistant to salt. They do not outgas during curing, so the film thickness can be up to .020” without bubbling or cracking. Disadvantages are that they aren’t smooth with thin finishes, and they’re less solvent resistant than urethane finishes.
Polyurethane – These coatings have excellent weather resistance and are very resistant to scratches and chips. These are best for outdoor applications. They’re resistant to acids, salts, grease, oils, humidity and corrosion. You can get nice glosses or good matte finishes. Disadvantages are that they produce volatiles upon curing thus limiting thick film formation. However, you can bake on several layers to get thick films without fear of bubbling from volatiles.
Epoxy – These coatings are good where flexibility, corrosion resistance, and toughness apply. They are more likely to stick to materials that other powders won’t stick to. They don’t outgas, so films can be .1” thick or greater if desired. They have good corrosion resistance and excellent chemical resistance. These are harder than polyurethane, but are severely limited in outdoor use due to their poor ultra-violet light resistance. They also yellow if cured for too long.
Hybrid – These are a mix of technology between epoxy and polyester. These powders are softer than epoxy and still have poor UV resistance so are recommended only for indoor use. They are typically a good primer coat. Hybrid powders outgas a little, so are limited to about .020” thickness.
High Temp – These silicone based powders are offered in relatively few colors, but are suitable for use in high temperature environments. Primary uses are for grills, stoves, engines, and furnaces. Cure temperature is the same as for most other powders, but the coat is resistant to 1000°F
Types of Coats
Powders may be coated over as many times as you like to produce the desired film thickness. Some powders require topcoats for protection. Opaque coatings usually don’t require topcoats and will be fine as is. Metallic coatings (very nice looking) usually require topcoats for added protection. TGIC or Urethane topcoats are suggested except over high temp coatings.
Air Compressor with regulator down to 10-15 psi
Powder – your desired color, sheen, and type for the application
Respirator – powder is itty bitty and nasty to breathe, great opportunity to use your N100 mask
Oven or Heat Lamp – oven is easiest, but should NEVER be used for food after powder coating
Powder coating procedure
Prep for powder coat is similar to painting. Clean the surface to get any oil or residue off. Sand and polish if only using clear topcoat on bare metal (this can look really good). Sand the surface to make sure any rust has been cleaned off. Always sand aluminum to get the layer of aluminum-oxide off. Then clean with alcohol or other solvent and let dry. If you want powder only to go certain places, use high temp masking tape to mask off the area. If you’re protecting screw threads, then just put a screw/bolt in to protect the hole.
Once your part is dry, take it and place it on or hang it from the oven rack. If you’re using a heat lamp, find a way to hang it or something to set it on that won’t move or be affected by heat.
Pre heat the oven or heat lamp now so it’s ready when you’re done coating. Use the cure schedule prescribed on the powder you’re using. They are generally quite forgiving though.
Now find an area that is wind free, but is okay to get dirty. Powder will go on the floor. If you clean well prior to spraying, you can sweep and reuse the powder from the floor! Set up the gun here and get your footswitch in a convenient place. Make certain that there is no gasoline or explosives nearby as the gun could create sparks.
Attach the ground clip to the part directly, the wire where the part is hanging from, or to the oven rack provided it will make electrical contact with the part to be coated. Make sure your setup here will be easy to move to the oven or heat lamp.
Put on your respirator and safety glasses.
Shake the powder in its original container to stir it up. Wait two minutes for the dust to settle in the container, then open it and dump a reasonable amount into the powder gun’s powder cup. This amount is usually a lot more than you plan on using. If you don’t dump enough in, then gun won’t spray much powder and it will take a long time to get a nice thick coat on your part. Screw on the cup to the gun.
Now hook up the power to the base unit, turn it on, and plug in the air. You’re ready to go but first make sure you Don’t Touch The Tip of The Gun. It’s charged with 50,000 Volts and will probably kill you in a rather unpleasant fashion.
Now, hit the footswitch and hold it down then spray the part from a foot away. The particles should go towards the part and land on it evenly. If few particles do or they don’t seem to stick well, you may have a grounding problem. Coat the part everywhere you want powder and get it to the desired thickness.
Once you’re done spraying, kick off the footswitch and shut off the base unit. Then, still holding the gun in your hand, unclip the ground wire and while touching the insulation, touch the ground clip to the tip of the gun, it should spark. Touch a few more times to make certain there is no residual voltage on the gun. Now carefully take your parts to the oven for curing.
Try to avoid dust from landing on the parts, but most importantly don’t touch them as you’ll smudge the finish. If you messed up the coat before curing it, just brush the powder off and clean again with solvent.
Open up your oven and slide the rack gently inside, or set up your heat lamp to heat the part to the cure temperature. Wait the required time after the powder glosses over. Pull your parts out, let them cool and you’re finished. Now they look great and you’ll want to coat everything you have that’s made of metal!
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