Tool Tutorial

Powder Coating

Safety and Procedures
•

Dustproof safety goggles and a NIOSH-approved respirator are recommended
•

Powder coating system must be plugged into a properly grounded three-prong outlet
•

Never touch the tip of the gun to the part while coating it. This may cause a painful static
 discharge or even ignite the powder coating media
•

Powder coating dust can ignite, so do not coat parts near an open flame
•

The powder coating system uses extremely high voltages so members with pacemakers are
 not allowedpermitted to use the systemsystem.

at TechShop
•

Typical curing temperatures are around 400 degrees F. Anything that cannot handle such
 temperatures (rubber seals, grease, paint, etc.) must be removed before putting it in the oven

 

Overview

Overview
While powder coating seems like a relatively recent invention, it has been around for about 50 years.
 Powder coating yields a superior finish with excellent durability. Powder coating is recognized as an
 environmentally friendly method of applying a quality finish. Unlike paint, powder coating releases
 almost no volatile organic compounds (VOCs) into the environment. The powder is easily cleaned up
with a broom and dust pan or vacuum cleaner.

Powder coating is a process in which a dry, powdered polyester resin is sprayed on to the item to be
 coated. The powder is positively charged as it exits the powder coating gun. The item to be coated
 is grounded and attracts the positively charged particles to the surface. Once cured in an oven, the
 surface is smooth and tough.

Virtually any type of metal can be powder coated, including steel, aluminum, magnesium, cast iron,
 brass, copper, bronze and titanium.

The key to a long-lasting and good-looking finish is the preparation of the metal. The best way to
 prep the surface is by abrasive blasting it down to bare metal with aluminum oxide or glass beads.
 Once the part is bare metal, the part is washed with a chemical cleaner to remove any dirt or leftover
 abrasive from the blasting process. The part is then baked in the oven for a short period to fully dry it
 before coating it.

Part Prep: Abrasive Blasting

https://wiki.protohaven.org/books/tool-guides/page/sandblaster-tool-tutorial
The abrasive blast cabinet works by using compressed air across the top of a tube to draw the
abrasive media up from the bottom of the blast cabinet. Media enters the air stream where it is forced
at high speed towards the work piece. The rate that material is removed can be changed by adjusting
the air pressure to the blaster, holding the blaster closer or farther away from your work piece, or
changing the media type. TechShop keeps 60 or 80 grit aluminum oxide in the blast cabinet, but
walnut shells and glass beads are also available, which tend to be less abrasive.
Abrasive blasting cleans paint, rust or corrosion, and other finishes from the part quickly and easily.
1. ConnectSee anour airSandblaster supplyTool to the regulator. Set the pressure using the adjustment screw. Ninety
psi is goodTutorial for steel parts, while 45 psi works well for aluminum.
2. Open the doordetails on the end of the cabinet by
releasing the two latches and placesandblasting your part
inside. Make sure your part has been cleaned
of dirt and grease and dried before blasting it.
3. Flip the switch on top of the cabinet to turn
on the lights and start up the vacuum. The
vacuum helps keep down the dust generated
by the blasting operation.
4. Put your hands into the gloves on the front.
5. Locate your part in the machine and hold it
securely. The flat surface of the part should be
about 45 degrees to the abrasive gun.part.

 

Part Prep: Chemical Cleaning

Once the item has been cleaned down to bare metal, it will need a chemical cleaning. The chemical
 cleaning helps remove any dust or other media left over from the abrasive blasting as well as any
 skin oils left where you may have picked up the part with your bare hands. Clean steel parts with an
 alkaline cleaner such as soda ash or trisodium phosphate
 (TSP), while aluminum, brass and zinc may be cleaned with
 Simple Green.
1.

1. Preheat the powder coating oven to the temperature
    specified by your powder media. See our Powder Coating Oven Tool Tutorial for details.
   2.
2. Fashion hooks from steel wire to hang your part from
    in both the paint booth and the powder coating oven.
    Once your part is clean, you don’t want to get any
    oils on it that may make for a poor finish.
   3.
3. Rinse your part under running water thoroughly.
    Spray it generously with the appropriate cleaner,
   scrub it well with a brush, and then rinse it
    thoroughly under running water again.
   4.
4. Holding the part by the hook, hang the part in
    the preheated powder coating oven for five to 30
    minutes, depending on the size, thickness and
    porousness of your part. Open the oven door slowly
    to avoid a blast of hot air in your face.

 

Powder Coating Setup

While your part is drying out in the oven, it’s a good time to get the powder coating gun and
 surrounding area set up.

Make

sure
1. Turn on the areabooth you’lllights
be
2. Connect coating in is clean and
   free of dust. Use a compressedthe air blowhose gun(on the wall) to get
   anythe loosecontrol dustbox off(via the spraytransparent booth.
   2.tube)
3. Turn the control box on
4. With no powder loaded, confirm the control box has correct KVA and air pressure:
5. Remove the powder coating gun from theits kit and
   use the blow gun to clean any leftover powder from
   previous users.
   3. Connect the compressed air supply to the regulator,
   connect the powder coating gun to the regulator,
   and open any closed valves to supply air to the
   powder coating gun.
   4. Pull the triggerholster and adjust the regulator to between
   10 and 15 psi.

   Fill the powder cup about 1/3 of the way with powder
   and attachbring it to the gun.control Overfillingbox

can
6. Point resultthe gun away from you and any electronics, then squeeze the trigger
7. Adjust the displayed air pressure to between 2-4 PSI
8. Adjust the KVA as recommended by your powder's spec sheet (default: 70KVA)
9. Replace the powder gun in an
   undesirableits holster
10. Inspect the gun, ground clamp wires, and other areas of the booth for leftover powder streamand thatperform mayany leavemissed unsightly
    lumpscleanup steps as needed to prevent cross-contamination.
11. Insert your powder into the cup (no more than 1/3 full)
12. Screw the cup into the lid that's mounted on yourthe part.
    6.side of the booth.
13. Turn on the air filter
14. Test the spray pattern of the powder coating gun. It
     should come out in a light fog. Adjust the air pressure
     as necessary.

Powder Application

TODO picture of powder coating controls

Once your parts have dried and the powder coating gun is set up, you can remove your part from the
oven and powder coat it.
1.

1. Open the over door slowly, use a pair of heat resistant gloves to remove your part from the
    oven, and hang it in the spray booth. If you have any masking to do, let your part cool before
    applying any tape.
   2.
Plug in the powder coating gun and attach
2. Attach the ground lead
    to something metal that makes a complete circuit to your
    part. Since powder coating is an electrostatic process, it’s
    very important that the part be properly grounded. If
    powder does not stick to your part, then it’s likely the part
    is not well grounded.
   3.
3. Move the tip of the gun to between six and 12 inches from
    your part, click the voltage switch and pull the trigger,
    and move the gun to apply powder to your part. Similar
    to using spray paint, keep the gun moving while applying
    powder to make an even coat.

 

SAFETY NOTE: The tip of the powder coating gun is holding a
 very high voltage charge. Due to this high voltage, it is extremely
 important that you do not bring the tip of the gun too close to the
 grounded part. 

At distances less than six inches, electricity may arc between the gun and part. If powder is being
 applied when an arc occurs, it could result in a flash fire of powder.
 If this happens, immediately release the voltage switch and trigger to stop the flow of powder. Unplug
the powder coating gun and clean any fused powder from the gun. You may also have to remove fused
 powder from the part.

Curing

Curing
Once your part is coated, it will need to be placed in the oven. Each powder has different cure times
 and temperatures, so be sure to read the directions carefully.
1.carefully - see our Powder Coating Oven Tool Tutorial for details.

Transfer your part from the spray booth to the oven. Be careful, since knocking parts into each
 other may create a poor finish.

 

Applying a Second Coat

When applying a second coat or re-coating a part, modifications in equipment settings and/or
 technique are needed. The electrostatic charge should be reduced (either by lowering voltage or
 limiting current) and/or the gun-to-part distance should be increased.

Be aware that the application
 will require more time. The equipment will not be as efficient (i.e., transfer efficiency will decrease
 when doing re-coats), but the application can be achieved. Sanding the base coat prior to powder
 application can aid in second-coat adhesion.

Applying a second coat to a part that has a cured powder coat finish requires adjustments in charge
 setting, time and technique. With patience and proper technique, you should be able to achieve the
 finish you desire.

Coating Hot Parts

Powders can be applied to hot surfaces. To use this technique, pre-heat the part to cure temp, 10
 to 40 minutes, depending on size. After pre-heating, remove part from oven and immediately apply
 powder.

You will notice that powder will flow immediately upon contact. Exercise care to avoid drips
 and runs.

Place coated part back into pre-heated oven set at cure temp for an additional 20 minutes
 to complete the cure.

Cleanup
1.

Turn

Keep the powderair coatingfilter gunrunning OFFduring andcleanup unplugto itcontain fromairborne powder!

1. Turn off the wall.
   2.control box.
2. Detach the cup, return remaining powder to your supply, then wash and dry thoroughly. Store the cup andupside-down pour any unused powder back intoon the originalconical container.
   3.drying Userack next to the compressedcontrol airbox.
blow gun to blow any unused powder out of the feed lines, gun and
powder cup. Be careful to always blow powder away from yourself.
4.
3. Detach the air supplyhose from the control box. With the air filter running, use the air hose in a sweeping motion to push any loose powder towards the filter at the back of the booth.
4. Place the gun on the floor and oriented towards the rear wall, then use the air hose to blow air into the intake of the powder gun (the larger opening in the cup mount) for 2-3 seconds to eject remaining powder from the line.
5. Using a slightly damp paper towel, wipe down  any loose powder on the ground clamp, cable, and all surfaces of the powder gun and its hoses. Holster the powder gun.
6. Use the shop vac to clean up any remaining loose powder from the filter, booth walls, floor, powder cup mount area, ground clamp and cable, and anywhere else you find it.
7. Turn off the booth light and the powderair coatingfiltration gun from the regulator. Put the gunsystem, and gloves
   backtidy inup theany kitcables.
box

and return them to the front desk.

 

Care of the Finished Part

A powder coated finish requires very little care. Powder coating produces a very scratch resistant
 finish.

If you get scratches in a powder coated finish, gently sand the affected area with 600-1000
 grit wet sandpaper. Then use a buffing wheel with appropriate compound to remove the sandpaper
 scratches and achieve your desired shine. Generally, waxing is not recommended for powder coated
 finishes. If you contaminate the powder finish with waxwax, you,you can no longer re-coat the part with
powder and will have to strip the part back to bare metal and start over.

Removing Powder Coating

Most organic solvents (acetone, thinners, etc.) are completely ineffective for removing powder coated
 finishes. Aircraft remover is generally effective at removing powder coating, as is abrasive blasting,
 though this is a time-consuming process due to the adhesion quality of powder.

Troubleshooting Tips

Pitted Finish
1.

1. Make sure the gun is thoroughly cleaned before starting or changing to another powder.
   2.
2. Make sure the part is completely cleaned of all contaminants.
   3.
3. After cooling, wet sand the areas with 600-1000 grit to level the pits. A second coat of powder
    can then be applied to the entire part.
   

Coating Porous Materials

In some cases, contaminants in porous materials will cause pits in the powder. Porous cast iron, die-
cast metal, cast aluminum, and magnesium parts trap contaminants that outgas when heated and
 cause porosity problems as the powder is curing. To avoid this, preheat the part to 400°F for 30-60
 minutes.
Note:

Die-cast metal and solders vary widely in formulation, many of which can be difficult to powder
 coat and, in some cases, may even melt at the 400°F typically used to cure most powder coat media.

Orange Peel

Orange peel is when the coated surface resembles the surface texture of an orange or other citrus
 fruit. A certain amount of orange peel is unavoidable, especially with polyester-based powders.

Orange peel can often be removed by sanding the part with 400-600 grit sand paper (wet or dry) and
 then buffing the part to achieve a good shine.

The main causes of orange peel are insufficient coating, over-baking or excessive powder buildup.
 Powder buildup is easy to see because the powder will start to stand on its end like hair. If this
 happens, stop applying powder and, with light air pressure, blow off some of the powder.
 If the powder does not apply evenly, replace moisture trap on the gun and use fresh powder.

Poor Spray Pattern

If the gun does not spray, the air pressure could be too low or moisture may be clogging the filter. The
 level of powder in the cup should be at least one inch deep to flow efficiently through the gun.

No Coverage or Poor Coverage in Recessed Areas

Hold the gun so that the side or peripheral discharge of powder goes into crevices, recesses and
 sharp angles. Exercise care to maintain at least a six-inch clearance from the part being coated in
 order to avoid an arc.