Jun 10, 2016 0 comment

“I am planning on powder coating an electric motor. The motor has an aluminum case, steel covers with a conversion coating on them, and a steel armature shell that is pre-painted. The motor is not sealed and therefore cannot be washed. What would be my pretreatment options? The motors come clean from the supplier, but is that clean enough for a powder finish? “

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“You raise an interesting question, How clean is clean enough for powder coating? Liquid coatings that contain petrochemical solvents can “bite through” light oils left on the part`s surface to provide adequate adhesion. Since powder coatings do not contain any solvent, residual oils left on the part surface can be an impediment to proper adhesion. Furthermore, organic soils (such as oil) can bleed through light colored powder coatings under the high heat conditions experienced during the cure cycle. For these reasons it has always been good practice to scrupulously clean the surface prior to applying any powder coating.”

“However, cleaning requirements can be less critical if the powder coated product does not have high quality appearance and adhesion standards. The coating performance depends upon perceived quality requirements and will dictate the appropriate process requirements. This fact is proved in the automotive industry where under carriage parts have a 336 hour salt spray corrosion requirement and the body parts have a 1,000+ hour salt spray requirement. In this case, the automotive companies sense that their customers will accept rust in short order on the car`s suspension springs but not on the car`s fenders. Therefore under carriage parts are pretreated much differently than body parts. Using the same pretreatment for all parts will ensure that either the body parts will not perform up to expectations or the under carriage parts will be too costly to manufacture.”

“How clean your motor housings need to be is dependent upon what your customer expects from the powder coated finish. Understanding this requirement is paramount for determining the appropriate finishing process. You have several options to clean your motor parts prior to applying the powder coating:

  • Do not clean the motors at all. This may provide an adequate solution since the parts are cleaned and pretreated prior to arriving at your facility. Use clean lint-free gloves to handle the parts prior to powder coating. Remove any loose contaminants such as dust and dirt before coating.
  • Use a vapor degreaser to remove any residual soils on the parts prior to powder coating. This method of cleaning has been under scrutiny by the EPA, so be sure you are in compliance with all federal, state, and local statutes.
  • You can solvent wipe these parts prior to coating. Be aware that this method is suitable for lightly soiled substrates. Change your wiping rag often to prevent reapplying the oils. OSHA, EPA, and the local Fire Marshall closely watch this method of cleaning, so be sure that you have plenty of ventilation and are in compliance with all other safety and disposal requirements.”

“Try a test batch of products to ensure that the chosen method will work consistently in your facility. Check the parts for proper adhesion after they are fully cured. Also, be sure to run any performance tests your customer may require on these motor housings. If the test results are acceptable, then you have a successful powder coating process.”

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