Testing of the Sears Powder Coating Gun

Variable Speed Self Contained Blower Model

 

Copyright 2005 by James P. Riser

 

 

 

This page will describe some testing I did with the new Sears Craftsman Powder Coating System.

The system includes the gun, one color cup, transformer, high temperature masking tape, high temperature plugs, hooks, and a plastic case.

The Sears powder coating material is supplied in small bags.

The powder in each bag should cover up to 7 square feet of surface.

I have purchased a variety of powders for testing from Columbia Coatings

I wanted a powder coating system that I could run without turning on my noisy air compressor. So I thought I would try the new Sears Powder Coating System. It was on sale - so I decided to act now!

Since I only manufacture rather small items, I require only a smaller size of oven for curing the powder on many items. Fortunately I discovered a toaster oven at Walmart for less than $13! This was about what I wanted to spend on such an oven. In addition to small size, I wanted a window in the door so that I could monitor the curing process. This little oven even has a timer on it to shut down the elements after up to 15 minutes. If I like everything, I'll pick up a larger oven for quantity production.

This is the $13 toaster oven I selected for my use.

Here is the oven "on" during the curing process.

 

The sample to be powder coated is a small spun copper dish (similar to the products I will want to powder coat).

Here is a close up view of curing in operation - the powder has begun to flow.

The copper was sanded down to bare metal and cleaned off with lacquer thinner. The coating I selected is a textured coating with black and gold flecks.

 

 

I did not clean the scrap steel plate used to support the dish; but it also ended up with a nice coating.

 

Here is another view. There are three layers of coating on this test sample.

I applied the three layers in this manner: 1st layer as usual; 2nd layer as soon as the powder began to flow; 3rd layer when the second layer began to flow.

This will give you an idea of the size involved.

I am very pleased with the new Sears equipment. The finished coating is very professional looking. This system will definitely meet my needs.

Here is additional testing on a 3" diameter aluminum disc about 1/4" thick.

I machined the surface and smoothed with a 150 grit abrasive pad using oil.

The rim of the disc was lightly filed then sanded. I wanted a surface for the powder to adhere to and I wanted to determine if the machining would still be visible.

This disc was supported by a smaller disc to raise it up off of the support steel plate.

The ground wire was clamped to the supporting steel plate.

The gun power was attached - to charge the powder as it passes the tip electrode.

The powder after being applied by the gun.

The powder is only held on to the metal by static electricity.

 

Things look like this as the disc is placed into the preheated oven.

Notice that the powder looks like fine grit.

 

 

 

Once the disc comes up to temperature, the powder begins to flow.

 

The flow continues with the surface becoming smoother.

 

When the metal was at temperature and the flow smoothed out, I set the timer for 15 minutes.

 

This is how things looked when the powder was fully cured.  

 

Here is a comparison between the two tested objects. The three step layer on the thin copper dish is much finer grained.

The coating on the thicker aluminum disc is much more textured and the gold veining more pronounced.

Both are professional looking and feeling coatings.

 

 

 

 

A Test of Transparent blue Powder

One of the colors that I want to use is a transparent blue.

This is how it comes from Columbia Coatings

 

I have added an oven thermometer to my setup.

 

This aluminum cylinder is to be powder coated for this test.

Notice the blemishes on the top. I wanted to determine how "sloppy" I could be and still get a good coating.

After cleaning the cylinder with lacquer thinner, I set it in the oven to preheat.

Columbia Coatings indicates that this powder should be used over their chrome base coat; but I wanted to see how it would look over semi polished aluminum without the chrome base coat.

The transparent blue powder was poured into the color cup.

The applied powder looked like this...

There is always a little blowby of powder onto the gun.

This stray powder can be quickly removed with a good blow or with a damp towel.

The still warm cylinder was returned to the oven.

After a few minutes at between 375 and 400 degrees, the powder begins to flow.

 

When fully cured (around 20-25 minutes), the cylinder looks like this.

The coating is beautiful - except for where I made a few mistakes. I coated outdoors and just when I began to spray the powder, the wind kicked up. A few specs of dust found their way onto the cylinder top as the powder was sprayed. You can also see traces in the coating from lint (from the paper towel I used to clean the cylinder - lint free cloth towel from now on). Also the original blemishes left on the semi polished cylinder for testing do show through. A higher degree of buffing would have taken care of this problem. Defects can be seen in the image below. This is the surface with the problems.

I also was interested in seeing if I could buff up the aluminum right next to the powder coating without ruining the coating. This can not be done with a painted item.

Here is the same cylinder after I polished the rim on my buffer.

 

And a close-up of the line between the newly polished top and the coating. Smooth!

 

I also wanted to test the coating for flexibility - so I bent the plate that was supporting the cylinder.

 

Conclusions:

1. The Sears syatem works.

2. This system works with powders from other suppliers.

3. Surface prep is critical - especially for transparent coatings.

4. Do not try to powder coat in the dusty wind.

5. The coatings are tough yet flexible.

6. With a well buffed finish the Columbia Coatings transparent powders should work well - even without the chrome base coat.

In conclusion, I feel that the new Sears syatem can provide the home shop worker with a viable powder coating method.

New addition!!!

Since I am running a small business, I wanted to do powder coating on several of the items that I manufacture. The small toaster oven was fine for testing and a few one-of-a-kind items; but too small for production purposes. So when I received a 20% off coupon from Harbor freight, I decided to finally get one of their powder coating ovens (made in India). I considered converting an old kitchen oven into a powder coating oven; but wanted to stick with 110 voltage as I would be moving things around in the shop and 220 might not be where it was needed for an oven. In addition, this looks better.

This is what the oven looks like.

Here are the controls.

The interior circulating fan was a feature that I felt I wanted.

The interior is all stainless steel and comes with one rack and two hanging bars - fine for my needs.

The three heating elements are in the bottom of the oven.

Another feaure I wanted was the built in mercury thermometer.

This larger oven will make my work much easier. If interested, you may find the oven specs on the Harbor freight site.