Seeing the benefits of nitrogen

June 9, 2014
Using nitrogen in heavy-duty shops takes training and adjustment, but can increase product quality and cost savings.

In the heavy-duty collision repair world, we have to deal with products that are often best applied when warmed to 95 degrees. If you’ve ever sprayed commercial finishes, you’ve experienced the sticky overspray that seems to cling to everything and is strong enough to make your feet feel like they are glued to the floor. And it seems the planets must align in order for the metallic to layout properly on commercial finishes. Technique, air pressure, temperature, spray gun settings and solvent choice are just a few of the many variables that painters have to adjust daily in order to have a successful paint job.

On large jobs like these, savings from nitrogen really adds up.

It is entirely different from the automobile solvent coatings and waterborne technology of today. I know technicians have to deal with these issues in the car world, as well. However, commercial refinishing poses different challenges than automotive refinishing.  

The variables involved in painting heavy-duty vehicles — such as having to spray a metallic while dangling from scaffolding in order to paint the center of a high-top Peterbilt sleeper — can make the process exponentially more difficult. Luckily, about a year ago, we had the opportunity to try spraying with nitrogen. It has empowered us to take control of many of these variables.

Now, I’ve read many articles about using nitrogen, and they all sounded too good to be true. Many of those interviewed stated how easy it was to get up and running and how it saved thousands on material. For us, it wasn’t an easy transition. We were one of the first commercial refinishing heavy-duty shops in the country to try an ionized, heated, nitrogen system. We had to learn how to make it work for us. The support we received from the manufacturer was great, but it was uncharted waters for both of us. At that time, at least two of the other leading nitrogen system manufacturers had yet to work with a shop in heavy duty. 

Spraying a high solid commercial finish om a Kemworth W900 hood using ionized, heated nitrogen.

Before you consider nitrogen, I recommend that you create a solid baseline. You can’t expect a plug-and-play transition followed by paint savings if you’re not already using good practices. Create consistency among your painters with spray guns, spray tip sizes, spray gun control settings and air pressure. Make sure you have the proper air supply and hose fittings to provide enough air volume to your spray gun. Ensure your painters test their film thickness with a wet mil gauge card or a digital dry film thickness gauge. Try to control as many variables as you can to build a starting point. 

Testing Compressed Air versus Nitrogen using a low hiding yellow color.  The nitrogen proved to help the color cover more quickly.

Once we established our baseline and started using nitrogen, we continued to spray using our old techniques, pressures and spray tips. Problems arose. We were getting solvent pop because of too much paint on the panel. Mil thickness was almost twice the recommended amount. The finishes were looking “fluffy,” as there was too much material on the panel. We looked at several alternatives to fix the problems — adjusting the spray overlap, speeding up the spray passes, changing air pressure, using smaller tips and trying different solvent and reducer combinations. We found the solution involved a combination of changes; you will have to find out what works best in your shop. We continue to constantly tweak our system to squeeze out more savings and productivity.

Many commercial paint lines recommend a crisscross spray pattern, and our painters have been using the technique for well over a decade. They could paint a panel with their eyes closed because of the muscle memory they developed over time. It was very difficult for them to change from the pattern they have been accustomed to. Most of the painters adapted to spraying with the nitrogen, and they are thriving. Some painters would subconsciously revert back to their old, tried-and-true way of spraying in the middle of a big job, which caused some issues. Thankfully, they have adjusted over time. 

Nitrogen helps with metallic orientation.  We can make blends with touch metallic colors in the middle of flat panels.

The nitrogen system allowed us to limit Mother Nature’s influence on our production. We are able to utilize the slowest solvent and reducer packages regardless of outside temperatures. Slowing the paint down allows it to flow out to control texture and mottling. The hoses are heated and keep the nitrogen fluid carrier dialed in at a specific designated temperature. By changing temperatures and solvent packs, we can match the orange peel to adjacent panels with smooth or textured finishes. With compressed air, changing outside temperatures can make the air expand and contract, which requires spray gun or wall adjustments in order to achieve consistency. Because nitrogen is inert, the system basically allows the spray gun to be set at one pressure, and it never has to be changed again. Nitrogen doesn’t hold water, so moisture is kept out of the lines, which helps in reducing flash times. The combination of nitrogen and the heated lines allows the paint to get out of dust more quickly, and it has drastically reduced our need to buff. We also don’t buff as much because the Nitrogen System allows us to spray at lower pressures, which reduces static electricity and attracts less dust to the panel. We are able to move parts in and out of the booth faster and reassemble in much shorter times. Prior to nitrogen, it took half a day or overnight to move parts without finger printing, even after a bake cycle. We spray waterborne paint on the medium duty vehicles and cars. The nitrogen system really speeds dry time to just over a minute between coats.  It dries quickly even on hot humid days. 

One feature that our system has over most on the market is that it ionizes the fluid carrier and places a positive charge on it. Marketing materials for the ionization process claim that when you sand a panel, you are naturally creating friction and causing the panel to hold a negative charge (especially on fiberglass). The ionization places a positive charge on the paint, and when the paint hits the panel the opposites attract. The paint droplets tend to cling to the panel and themselves, instead of bouncing off the panel as overspray.

Nitrogen allows us to spray with smaller tips and at lower pressure which keeps overspray down allowing our booth to stay cleaner.

Competing nitrogen system distributors claim that ionization is a gimmick because after a positive charge is placed on the gas, it has to travel the length of the hose and go out the end of the gun, hence creating friction and taking away the positive charge. I can’t tell you if that is true or not. I can tell you that it must not hurt because we get very little dirt and are getting great coverage on the panel. I’m a believer. We paint several of the same type of hoods over and over again. If we look back on material usage from past jobs, we were easily using 25 percent or more on basecoat and clear. The savings are even higher on sealers and primers.   

One problem we continue to have is over mixing. We paint some very unusually shaped parts in the heavy-duty world, anything from a Peterbilt 379 to a 70-foot expandable drop deck trailer. We judge by gallons instead of ounces. Surface area can be hard to calculate. And blow by can add up if the rails and tubes are thin. When painting an all over in commercial paint, a job can be ruined if you have to stop and mix more because you may lose your wet edge. Painters tend to err on the side of caution, but it can get very expensive when a gallon of commercial paint could cost well over $1,000. However, we are getting better and better every day.

Determining return on investment has proved difficult in some cases. It should be easier as time goes on.  A basic system runs anywhere from $30,000-$60,000, depending on the brand. They increase in cost based on your need for more hoses and more spray booths. We have had a learning curve to deal with, but I’m starting to compare refinish labor hours sold in comparison to liquid costs from prior years and the trend is moving in the right direction. Our productivity has increased, and our quality is way up. Our buffer is gathering dust form very little use, and we do not have to change over our spray booth filters nearly as much. It has cut maintenance cost and time in half, if not more. In the past, it would take an entire day to wash down one spray cabin’s walls and grates, scrape off overspray and sweep out our concrete pits.  Now, we can get it done in half a day, and we do it less frequently. 

Prior to nitrogen, when spraying a large job, our downdraft booth floor would be the same color as the vehicle we painted, and you would struggle to lift your feet off the ground because the floors would be so sticky from overspray. With nitrogen, you would be hard pressed to figure out what color we just sprayed unless you looked closely at the filters. We have been extremely impressed with the results. I can’t say enough good things about making the change — our painters love it, and we are very proud of the product it enables us to produce.

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