Coating Weight Measurement
Coatings are applied to substrate materials for many reasons, including corrosion/environmental protection, wear resistance, chemical resistance, enhanced electrical conductivity, improved adhesion, aesthetics, and other purposes. The amount of coating applied to a product over a given surface area can be determined by calculating the coating weight. The total coating layer thickness used varies based on the application. Relative applications of coatings are most commonly found in automotive, appliance, aerospace, and medical industries.
Coating Weight is determined on a test panel or part with a measurable surface area. Most determinations rely on chemically removing or dissolving the coating without affecting the substrate material. A simplified method for evaluating coating weight consists of first weighing a test piece and then soaking it in an acidic solution to chemically remove the coating. Test variables include temperature, time, and acid concentrations, and are dependent upon the coating material. After soaking it in the solution, the sample is weighed again and the coating weight loss is calculated relative to the original surface area. In some cases, the stripping solution is collected and chemically analyzed via inductively coupled plasma (ICP).
More complex methods to determine coating weight involve the use of multiple steps to strip a coating. One method in particular includes the submersion of the test piece into a hot sodium hydroxide solution to create a reacting with the coating. The piece is then scrubbed and immersed briefly into hydrochloric acid to remove the chemically modified coating. This process is repeated until no reaction occurs and only base metal remains. PES is capable of performing coating weight loss for a variety of metallic coating/substrate combinations.
Common application specifications pertaining to coating weight loss measurement include:
Manufacturer's specifications and internal procedures
Entry Originally Posted in March 2021