Issue link: http://www.e-digitaleditions.com/i/901126
Unreasonable expectations for powder coated metal products Powder coating finish, when properly selected and properly applied in accor- dance with a comprehensive pretreat- ment and finishing specification, can extend the protective and decorative value of a variety of products that are manufactured from metals. Unfortu- nately, the simplicity of this statement is often exaggerated by overzealous indi- viduals and companies that aggressively promote the finish quality attributes of their products that are powder coated. The fact that a metal product has been powder coated does not mean that the finish on the product will last forever without change. It is a simple certainty that all organic finishes will change over time as they age and are stressed by the environment in which they are exposed. This should not be news to anyone read- ing this article. We all have witnessed coating degrade over time on products that we have purchased that are expected to last for years when exposed to weather. For example, our homes need to be repainted every five to seven years for protection from environmental degrada- tion and to keep them looking good if we want our investment to retain its value. The popularity of powder coating as a robust finish applied to products used outdoors is ever growing and for good reason. Powder coating finishes for out- door use on products such as lawn furni- ture, car and truck parts, handrails, fences, gates, electrical enclosures, architectural building components, and playground equipment exist throughout the world. Metal products that are exposed to the stresses of exterior weather environments must be engineered to withstand the stresses caused by weather for a reasonable amount of time before they lose their pro- tective and decorative value. It is no secret that weather and environmental condi- tions are unpredictable and will certainly vary greatly in different locations. Organic finishes change as they age As stated, all organic finishes will change over time when exposed to the stresses of the environment. Previous arti- cles have been written that detail the fail- ure mode cause and effect of the many variables that exist for coated metal prod- ucts, including the design, metal alloy selection, fabrication techniques, surface preparation, organic material chemistry selection, and curing of the finish on metal products that are intended to sur- vive outdoors. Add these product design variables to the variations associated with environmental exposure and any reason- able person can understand why all organic coatings change as they age. Finishes on metal substrates exposed to the harmful effects of environmental conditions, namely moisture, pollution, and ultraviolet light, will contribute to the degradation of the decorative and protective values of organic finish. This change will happen in two basic ways: 1. Change in the protective value of the coating (corrosion protection of the metal substrate) 2. Change in the decorative value of the coating (appearance of the finish— color and gloss) To make matters more complicated is the perception and subjectivity of "accept- ability" and "service life" expectancy by the end user that they are entitled to a fin- ish that will last unchanged forever. For this reason, it is impossible to predict in terms of time how long a given finish will remain "acceptable" to the end user. Warranty claims for changes in the finish in terms of decorative and protective val- ues are commonly made by individuals that lack even the most basic understand- ing of the physical, surface, and environ- mental attributes of organic coatings applied to metal products. Finishing professionals understand that all organic coatings, when applied to metal substrates and exposed to the stress of weather conditions, will degrade to some degree over time and will eventually degrade to the point that the coating will no longer provide the protective and dec- orative values that they did when the coat- ing was new. Continuous testing is con- ducted by industry professionals, coating manufacturers, pretreatment chemical suppliers, and metallurgists to compare finishing stress for a variety of metal sub- strates, finishing materials, and finishing processes. The quality accept/reject crite- ria for corrosion protection and aesthetic values of various finishing material chemistries can be quantified and com- pared using test equipment, test methods, accelerated corrosion, and ultraviolet exposure testing, among others. The end user is rarely, if ever, concerned about this factual and historical data. They simply want to know how long the finish is guaranteed to last on the products they purchase. Consumers claim to know exactly what they expect, and believe wrongfully that they are entitled to always be right. Perhaps in the retail or restaurant business this point of view may be somewhat valid, but not in the world of metal finishing. Purchasing decisions should be factually based Time and time again we hear stories of disgruntled consumers that believe they have been duped by false advertisements regarding the finishes on powder coated steel parts that they have purchased. Sadly, there are some manufacturers of consumer products used outdoors that Coater's Corner Coater's Corner Michael W. Cravens Powder Finishing Consultants and IKON Powder Coating POWDER COATING, November 2017 19