Powder Coating Hopper Bottom Trailer

Powder Coated Paint Over Wet Paint

SPARTA ENGINEERING almost exclusively recommends a powder coated paint finish on all of our mobile equipment. We feel powder coating is superior to paint and is the best choice in terms of price and quality.  There are many advantages to powder coating our products over applying regular wet paint. I’ll start with explaining the process of powder coating and then outline the main advantages.

Powder Coating is the application of organic powder by electrostatic attraction to metal. Once cured by heat the finish is a smooth, hard skin. All processes are factory applied under controlled, stable conditions. This provides significant benefits over traditional wet painting” – Patrick Handlovsky, TIGER Drylac Canada Inc

Painting Process Overview:

  1. The first step in either painting process is to sandblast the product after fabrication is complete. Sandblasting is used to remove mill scale, oil, and rust which commonly comes on freshly manufactured steel. On projects getting repainted, sandblasting is used to remove any old coatings still on the product. The medium used for sandblasting can range widely from biodegradable options such as walnut shells to manufactured steel grit. Most mediums can be re-used a few times before disposal and each have their own advantages and specific applications. Sandblasting, strips all the surface oxidization off of steel so it will rust within hours when exposed to the correct atmosphere. Keeping this in mind, it will important for the product to stay inside a dry environment after it is sandblasted.
  2. The next stage is to start applying the powder. The operator will begin with a zink based primer which is applied through a special electrostatic or corona gun. The electrostatic gun applies a +charge to the powder as it is discharged from the gun. These positively charged powder particles are attracted to the negatively (grounded) work piece. This causes two interesting phenomenons that help the paint process. First, the powder is physically attracted to the work piece so there is minimal over spray.  Second, if you try and apply the powder coat too thick in an area, the density of the positive charge will actually repel the powder and prevent it from being applied too thick.
  3. Once the powder is applied evenly to the work piece, it is moved from the powder coating bay into the oven where it is heated up to gel the primer. It is important to note that you will need a plan to move the product around gently as the powder is not adhered to the work piece (it clings using static electricity). Touching it or bumping the work piece too hard will cause a defect in the finish. The work piece will stay in the oven for a predetermined amount of time which is based on volume of steel being heated.
  4. After the primer is heated up or “gelled” it is moved back into the powder coating booth where the finish coat is applied. The final coat is usually a customer-driven color and is applied in the same manner as the primer.
  5. The last stage is to bake the product in the oven until it is completely cured and ready to go to the next stage of manufacturing.

There are many benefits to powder coating products over traditional wet paint techniques. At Sparta, we exclusively use powder coating on our products.

Top 5 Reasons to Powder Coat Your Products:

  1. Economics – The economic benefits of powder coating are numerous but the largest benefit has to do with efficiency and overspray. The average transfer efficiency of powder coating is 60-70% and any over spray is a solid and can be reclaimed and re-used netting virtually no wasted product. With liquid paint you have a transfer efficiency of 30-35%, roughly 50% of the product is evaporated and there is no possibility of reclaiming over spray. The base product for powder coating is also substantially cheaper than wet paint.
  2. Safety – Safely applying powder coating requires precautionary measures to avoid breathing in the powder and getting it on your skin. This is an easier task to manage since the product is a solid and inert (it doesn’t pose a health risk when not being sprayed). During application it is recommended to stay out of the application zone and to avoid getting it on your skin (because of the minimal overspray this is completely manageable). The product does not contain harmful chemicals such as solvents or volatile organic compounds (VOC) that are often found in wet paint.
  3. Environmental – There are many environmental advantages of powder coating as well. Since there are no solvents or VOCs there is no damage to the environment during application. The waste is also not hazardous and can be disposed in the landfill. Wet paint contains harmful chemicals that have been proven to deplete the ozone and produces hazardous waste that needs to be disposed of in an appropriate manner.
  4. Mechanical – Powder coating generally produces a coating twice as thick as standard paint.  The real advantage is its flexibility and ability to bend and yield with the material it is applied to. This makes it ideal in the transportation industry where the products are subject to a lot of vibration and twisting as they move down the road. We have also found that they stand up way better to rock chips and other common road damage.
    • Powder is not bullet-proof but it is more durable than its liquid counterpart.  In a nutshell:  It takes a lot more energy to put powder on and consequently it is more durable then liquid coatings which are air dry, no oven – “easy on, easy off”). 

      When liquid guys come in to our lab the one thing they are amazed by is the impact resistance and durability of powder.  You can bend a Q Panel in half and the powder doesn’t splinter off. – Duncan Alexander Spectrum Powder

  5. Production Advantages – The main advantage from a production point of view is that when the powder coated product comes out of the oven it is completely cured within 20min and ready to be put to work. Standard liquid paints can take days to completely cure and depend on the atmospheric conditions. You can literally put a powder coated object to work while it is still too hot to touch and not have to worry about wrecking the paint. Also in terms of production efficiency, with less waste over spray and less risk for runs and other defects, powder coating has become less of an art and a necessary skill taught to production staff.

The Downside of Powder Coating:

There is no doubt that I am all for powder coating but it wouldn’t be fair not to mention the few down sides of the process. The main concerns with powder coating are:

  • it can be difficult to match metallic paint colors
  • the start-up cost and cost of keeping an oven running are high
  • you can not paint on a rubber product because it will melt the rubber
  • you cannot touch up the same way you can with wet paint

Some of these problems can be overcome through design and engineering. By carefully designing a project before production and using 3D modeling to help visualize components, there is really no reason to have to weld or cut any parts after powder coating. Also, if you have engineers familiar with designing for final assembly, you can usually overcome any hurdles and make the powder coating process seamless and efficient.

Powder Coating Product Ready for Powder

Example of blasted product ready for powder

Powder Coating Reclaiming System

Example of powder reclaiming system

When I review the pros and cons of powder coating versus wet paint it seems like a no brainer to use powder coating to protect our products. Shoot me an email if you have any questions or leave a comment and I will get back to you.