I had made this toolbox in the Angular sheet metal class at Techshop. As it lay in the garage and gathered rust and mocked me, I knew I had to take the Sandblasting and Powder Coating class at Techshop to get a nice perfectly finished piece that was functional and that I could proudly display my tools in!
Right after I finished the class and was checked out in the equipment, I proceeded to reserve the equipment to finish my toolbox project.
Here you see the "before" and "after" pictures. Ok, fine, I'll stop tormenting you with this teaser and get on with the instructable already! :-)
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Step 1: Sandblasting the Piece to Get Rid of Rust and Prepare the Surface
First step was to sandblast the piece to remove the rust and prepare the surface for the powder coating.
The first picture shows the outside of the sandblaster, and the second photo shows the inside of the sandblaster. You stick your arms in to the gloves, and hold/move the piece with one hand while operating the sandblaster with the other, in a smooth sweeping motion about 3-4 inches away from the piece, at about a 45 degree angle. You will start to adjust your distance, angle and sweep to finesse it to get the best results.
The rest of the photos show the progression from untouched piece to final sandblasted piece. A remarkable transformation!
Step 2: Chemical Washing Your Piece to Further Prepare the Piece, Removing Oils Etc From Your Fingers
Next up, you will wash the piece with some chemicals (for mild steel, you use TSP (Tri sodium phosphate), or as in my case, a TSP substitute.
Remember to wear nitrile gloves - they serve two purposes - protect your hands, and also protect the cleaned piece from the oils in your hands! :-)
Spray on the product liberally, and then use a scrubbing brush to gently polish and clean the piece.
Step 3: Pre-baking
Next up, hang up the piece to dry a bit first. While it is hanging there, turn on the oven to 350 degrees (or whatever suitable temperature your powder coating says is optimal for it - read the label!). After the oven is at the correct temperature, place the piece in there for a few minutes to dry completely.
Step 4: Preparing the Powder Coating Equipment
While the piece is pre-baking, this is the perfect time to prepare your Powder Coating equipment.
Connect the ground wire to the iron rod from which you'll be hanging the piece.
The add some powder to the reservoir - fill it about 1/3rd - that'll be plenty of powder, and you'll most likely have a ton left over. Filling it more than a third will apparently not make the powder flow well, so I followed the advice!
Close the reservoir. Connect the central small diameter plastic tube to the main equipment. Use the rubber hose to connect the reservoir to the gun. Connect the air hose from the air supply to the main equipment.
Choose the nozzle you are going to use ( I used the standard nozzle as my piece was not too big) and fix it to the gun, and then clamp the end piece over the nozzle to secure it.
Make sure the air supply pressure is around 10-15 psi.
Now retrieve the piece from the oven, and hang it on the iron rod (which is grounded) with the metal hooks (that will conduct).
Turn on the equipment. Set the power to about 40 kv, and the air pressure to about 3 psi - adjust the regulator until you get a nice light fog.
Now you are ready to powder coat your piece.
Step 5: Powder Coating Your Piece
Keeping the nozzle a few inches away from the piece, turn on the gun and in nice smooth sweeping movements, coat the piece with the powder. The tip of the gun is holding a very high voltage charge. Do not get it too close to the piece, or it could arc, and that could result in a flash fire of powder.
The piece will get coated nicely with the powder in no time.
Reduce the kv to about half (20) to apply a second coat to smooth over the finish, if needed. Make sure you hit it from all angles and sides, and the piece is completely coated.
Step 6: Final Baking and Curing
In the final step, CAREFULLY move the piece to the oven. Since the powder is just electrostatically sticking to the piece, the coating can come off if you hit the piece or move it around too roughly.
Once in the oven, let it cure for about 10-40 minutes (depending on size - I gave mine about 20 minutes to be sure).
After it is done, hang it outside on the iron rod again to cool down.
And you're done!
Powder coating is an environmentally friendly method of applying a quality finish that is durable, and releases almost no volatile organic compounds (VOCs) into the environment.
And it looks pretty good too!
Hope you enjoyed this instructable. I made it at TechShop!