Why Consistent Coating Thickness Is Important

Why Consistent Coating Thickness Is Important

Sep 12th 2019

Of the many quality assurance tools that a coating services supplier should have on hand, coating thickness gauges are one of the most important for maintaining high-quality coatings that both perform properly and meet external standards. Another substantial benefit is cost savings, as keeping coatings consistently within specifications can reduce material and labor waste. And you should consider whether the time savings of a tester that measures continuously at 140 times per minute is worth the investment to prove your coatings are consistent.

Coating thickness gauges (aka paint meters or mil gauges) are used to measure dry film thickness without leaving marks on your parts. These are a “non-destructive testers” with great repeatability in measurements. Dry film thickness is probably the most critical measurement in the coatings industry because every coating has thickness range specifications. A coating thickness gauge provides vital information that can confirm the expected life of the substrate, the coating properties’ performance, the coating appearance, customer expectations, and the job’s compliance with international standards.

Managing Coating Expectations

Many jobs in the Military and Aerospace segments require verification of the work that you are performing. Suitable coating thickness gauges are certified by the all the applicable ASTM Standard test methodologies, which allows you to compete in markets that are sensitive to these specifications. Thickness testers can also compile the measurements you take and deliver a formal report that can be shared with the end user.

Most quality shops lay out pass/fail expectations of their customers before accepting their order, and more end users these days are requiring proof of testing. Coating thickness gauges demonstrate to your customers that the coatings were applied to the thickness they requested. This will help you eliminate rejects and take your customer satisfaction to new levels.

Incorporating thickness measurement into your everyday processes also saves on material costs. Monitoring coating thickness will drive your coaters to better control thickness and eliminate excessive wasted coating. As an example, if you purchase $10,000 in coatings a year and improve your thickness control by .5 mils, you would save $2,552 a year.

Save Money with Better Technique

By using these simple techniques, you'll be able to cut out the waste as well as achieve a better, more consistent finish for your Teflon™ industrial coatings.

  1. Plan of Attack: Have a plan before pulling the trigger. Plan to attack trouble spots and difficult to reach areas first.
  2. Spray Distance: The spray distance is based on the spray equipment, coating, complexity of the part, and spray environment. By keeping the gun at the same distance from the part the entire time you’re spraying, you can improve the consistency of the film thickness over the whole part. Increasing the gun distance increases the pattern fan size, and the coating thickness decreases as it is distributed over a larger area.
  3. Gun Angle: Maintain controlled gun angle to the part. Yaw and pitch spray angles will result in a non-uniform spray pattern distribution, causing inconsistent film thicknesses.
  4. Spray Pass Overlap: Each spray pass should overlap 50% to 75% of the previous pass. Overlapping below 50% results in “striping,” or variations in the film thickness. The more you increase the overlap, the thicker the coating, so overlapping above 75% requires more spray passes and more coating.
  5. Spray Pass Speed: Adjust the spray gun speed to achieve consistent films. Before pulling the trigger, consider the coating flow rate and the target wet film thickness. Adjust the equipment before spraying to find a flow rate that lets the applicator move at a controllable, comfortable speed. Spraying too fast can lead to decreased film thickness, and sometimes extra coats will be needed to make up the deficit.
  6. Trigger Control: Maintaining a consistent trigger pull on each spray pass directly impacts the flow rate, spray pattern size, and transfer efficiency. Start triggering immediately before the lead edge of the part and release the trigger immediately following the lag edge. Fully pulling the trigger provides constant flow rate control. The fluid knob on your spray gun can be adjusted to restrict the trigger travel distance so you can always pull the trigger all the way. Partial triggering, however, can be very useful for blending and touching up.
  7. Edge Banding: Partially pull the trigger to spray a light coat around the edges of the part. Then spray the center of the part, blending the edges into the first coat. Banding can increase transfer efficiency and increase film thickness on the edges. This technique ensures the edges get coated completely while maintaining consistent film thicknesses.

If you’re looking for more tips on keeping your Teflon™ coating services at the highest quality consistently, read our other blogs on “Basic Quality Testing” and “Advanced Quality Testing.”