11-13-2009, 04:18 PM
All you need to do beautiful powder coating is a powder gun system (available through Eastwood or J.C. Whitney) plus a compressor and an electric oven, and several wire coat-hangers. You can find an electric oven/stove somewhere in your neighborhood where a kitchen renovation is being done, or you can buy one at a used appliance store or Goodwill store for about $75.
Tip: You can't use a gas oven or barbecue grill. Flame can ignite loose powder! Also, don't use your kitchen oven because dropping powder will mess it up and there's a slight odor when curing. If you find a wall-type oven it will work quite well. If you find a range you can disconnect the top burners and use the surface for a work area.
What is Powder Coating?
Powder coating is another form of "painting," in which the metal being finished is coated with an electrostatically-charged epoxy powder and then baked at moderate temperatures to "cure" or fix the coating onto the metal. In general, powder coating provides superior adhesion to the metal and extremely smooth surface appearance. Its chief advantage is its fast application. Once applied and baked and then cooled, the part coated is ready for use. Painted items, on the other hand, require substantial time to dry and cure before use.
Developed for commercial applications in the late '60s, powder coatings initially replaced painting on such things as outdoor furniture, lighting fixtures, automotive components, architectural components and commercial signage. The coatings themselves are highly resistant to acids, alkali, mineral salts, fuel oils, alcohols, aromatic and aliphatic solvents and brake fluids. That makes them highly desirable in automotive applications.
All powders are thermoset plastics. That is, they cure from a powder state to a smooth surface coating as a function of temperature. The higher the temperature the shorter the cure time, but all of this is a function of how quickly the metal mass being coated comes up to temperature. Obviously, a cylinder head will take more time to bake than a generator bracket. In practice, curing a powder coated metal item is done at 400 degrees F for at least 20 minutes.
The powders themselves come in four overall types:
Epoxy Coatings are designed for electrostatic application, FDA compliance and low-cure baking capabilities. These powders offer very good surface quality and adhesion.
Hybrid Powder coatings have superior surface quality and excellent adhesion as well as flexibility and resistance to yellowing (due to overbaking).
Polyester-Urethane Powder coatings have the overall best surface appearance and weathering properties.
Polyester-TGIC Powder coatings have ultimate performance characteristics and are used commercially. They are generally not used by hobbyists due to cost and application considerations.
The type of powder hobbyists purchase is generally less relevant than the color. Powders are available in scores of colors and surface-types, but the color sometimes dictates the type of powder.
What Are Advantages And Disadvantages?
Powder coating a specific item is generally faster, start to finish, than painting the item, and there are fewer steps to the task. Powder coats, as stated above, are highly resistant to many of the things that mar or ruin painted finishes, and that resistance is "instantaneous" after baking. Painted surfaces, on the other hand, remain "soft" and easily damaged for days or weeks before air curing. Also, it is easier to obtain a smooth finish with powder coating than with multiple coats of paint. Less skill or practice is required. Part preparation is essentially the same as with painting.
Powder coating creates far less toxic effects than paint. No volatile solvents are used and the materials in powder should cause no significant skin irritation on short-term exposure. The only safety items recommended for powder coating are a good-fitting dust mask and latex (or nitrile or other type) gloves. Baking produces a slight plastic odor that some might find irritating, but there is no danger as long as there is normal ventilation in the work area.
Powders cost roughly $20 per pound, depending on color. Generally speaking, one pound of powder is equivalent to 8-10 cans of spray paint in coverage, making powder very cost-effective. It can be re-used (not all the powder adheres to the item) but is susceptible to contamination so care must be taken while spraying. (We find it isn't worth sweeping up and re-using)
There are a few disadvantages, however:
* Powders don't come in anywhere near the range of colors in which paints are available. They can be mixed to form other colors, but experimentation is tedious.
* Powder coating small items is time-consuming and sometimes not feasible. Once coated, items must be suspended inside the oven because wherever anything touches the powder will transfer off. Small fixtures, fasteners, etc. are difficult to powder coat and place in the oven.
* The most significant disadvantage of powder coating is that it can only be done on metal. The powder won't adhere to fillers or wood or other plastics, and most of these materials will melt in the oven.
How Is It Done?
We powder coated part of a Ford bumper jack to demonstrate how easy this is to do. The entire operation took less than one hour, and here's the step-by-step.
We sandblasted the part to remove rust and old paint, then wiped it clean with lacquer thinner to remove dust and any grease or foreign materials. We could have used soap and water and then dried the piece.
Photo 2 shows the piece, ready for coating
We then selected Ford Dark Blue as the powder color and loaded some into our gun's hopper with a spoon. We set our air compressor pressure at 10 psi and tested the gun and turned on the oven to 400 degrees.
We plugged in the powder gun, connected the ground to our part (in a spot where it wouldn't show later) and proceeded to spray the powder.
Once we had a good, even coating of powder on the part (we put on a relatively thick coat until the part looked like it was coated in velvet) we suspended it from a bent piece of coat-hanger wire that we had tested for fit in the oven before everything got heated up.
Photo 5 shows the part being inserted into the oven.
We set the oven timer for 25 minutes and when it went off we found a beautiful, blue finish on our jack piece. We removed it with pliers and, after 15 minutes of cooling, had a completely finished part, ready for installation in the trunk.
Conclusion
Powder coating is a cost-effective and worthwhile addition to any restorer's garage. It can't be used for all applications - especially large things like engine blocks and frames - and for specific color matching, but when appropriate it's a great way to go.
Tip: You can't use a gas oven or barbecue grill. Flame can ignite loose powder! Also, don't use your kitchen oven because dropping powder will mess it up and there's a slight odor when curing. If you find a wall-type oven it will work quite well. If you find a range you can disconnect the top burners and use the surface for a work area.
What is Powder Coating?
Powder coating is another form of "painting," in which the metal being finished is coated with an electrostatically-charged epoxy powder and then baked at moderate temperatures to "cure" or fix the coating onto the metal. In general, powder coating provides superior adhesion to the metal and extremely smooth surface appearance. Its chief advantage is its fast application. Once applied and baked and then cooled, the part coated is ready for use. Painted items, on the other hand, require substantial time to dry and cure before use.
Developed for commercial applications in the late '60s, powder coatings initially replaced painting on such things as outdoor furniture, lighting fixtures, automotive components, architectural components and commercial signage. The coatings themselves are highly resistant to acids, alkali, mineral salts, fuel oils, alcohols, aromatic and aliphatic solvents and brake fluids. That makes them highly desirable in automotive applications.
All powders are thermoset plastics. That is, they cure from a powder state to a smooth surface coating as a function of temperature. The higher the temperature the shorter the cure time, but all of this is a function of how quickly the metal mass being coated comes up to temperature. Obviously, a cylinder head will take more time to bake than a generator bracket. In practice, curing a powder coated metal item is done at 400 degrees F for at least 20 minutes.
The powders themselves come in four overall types:
Epoxy Coatings are designed for electrostatic application, FDA compliance and low-cure baking capabilities. These powders offer very good surface quality and adhesion.
Hybrid Powder coatings have superior surface quality and excellent adhesion as well as flexibility and resistance to yellowing (due to overbaking).
Polyester-Urethane Powder coatings have the overall best surface appearance and weathering properties.
Polyester-TGIC Powder coatings have ultimate performance characteristics and are used commercially. They are generally not used by hobbyists due to cost and application considerations.
The type of powder hobbyists purchase is generally less relevant than the color. Powders are available in scores of colors and surface-types, but the color sometimes dictates the type of powder.
What Are Advantages And Disadvantages?
Powder coating a specific item is generally faster, start to finish, than painting the item, and there are fewer steps to the task. Powder coats, as stated above, are highly resistant to many of the things that mar or ruin painted finishes, and that resistance is "instantaneous" after baking. Painted surfaces, on the other hand, remain "soft" and easily damaged for days or weeks before air curing. Also, it is easier to obtain a smooth finish with powder coating than with multiple coats of paint. Less skill or practice is required. Part preparation is essentially the same as with painting.
Powder coating creates far less toxic effects than paint. No volatile solvents are used and the materials in powder should cause no significant skin irritation on short-term exposure. The only safety items recommended for powder coating are a good-fitting dust mask and latex (or nitrile or other type) gloves. Baking produces a slight plastic odor that some might find irritating, but there is no danger as long as there is normal ventilation in the work area.
Powders cost roughly $20 per pound, depending on color. Generally speaking, one pound of powder is equivalent to 8-10 cans of spray paint in coverage, making powder very cost-effective. It can be re-used (not all the powder adheres to the item) but is susceptible to contamination so care must be taken while spraying. (We find it isn't worth sweeping up and re-using)
There are a few disadvantages, however:
* Powders don't come in anywhere near the range of colors in which paints are available. They can be mixed to form other colors, but experimentation is tedious.
* Powder coating small items is time-consuming and sometimes not feasible. Once coated, items must be suspended inside the oven because wherever anything touches the powder will transfer off. Small fixtures, fasteners, etc. are difficult to powder coat and place in the oven.
* The most significant disadvantage of powder coating is that it can only be done on metal. The powder won't adhere to fillers or wood or other plastics, and most of these materials will melt in the oven.
How Is It Done?
We powder coated part of a Ford bumper jack to demonstrate how easy this is to do. The entire operation took less than one hour, and here's the step-by-step.
We sandblasted the part to remove rust and old paint, then wiped it clean with lacquer thinner to remove dust and any grease or foreign materials. We could have used soap and water and then dried the piece.
Photo 2 shows the piece, ready for coating
We then selected Ford Dark Blue as the powder color and loaded some into our gun's hopper with a spoon. We set our air compressor pressure at 10 psi and tested the gun and turned on the oven to 400 degrees.
We plugged in the powder gun, connected the ground to our part (in a spot where it wouldn't show later) and proceeded to spray the powder.
Once we had a good, even coating of powder on the part (we put on a relatively thick coat until the part looked like it was coated in velvet) we suspended it from a bent piece of coat-hanger wire that we had tested for fit in the oven before everything got heated up.
Photo 5 shows the part being inserted into the oven.
We set the oven timer for 25 minutes and when it went off we found a beautiful, blue finish on our jack piece. We removed it with pliers and, after 15 minutes of cooling, had a completely finished part, ready for installation in the trunk.
Conclusion
Powder coating is a cost-effective and worthwhile addition to any restorer's garage. It can't be used for all applications - especially large things like engine blocks and frames - and for specific color matching, but when appropriate it's a great way to go.