Metal Finishing Guide Book

2013

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troubleshooting, testing & analysis CORROSION AND EXPOSURES – AN OUNCE OF TESTING IS WORTH A TON OF RECALLS BY BENJAMIN CARDENAS, ICP ANALYST/SALT SPRAY SPECIALIST; PHILIP SCHMIDT, CHEMICAL ANALYST/CORROSION SPECIALIST; AND MICHAEL PORFILIO, DIRECTOR OF OPERATIONS, ANDERSON LABORATORIES, INC., GREENDALE, WIS. There are many options for surface finishes when it comes to metal products. Chemical coatings and paints are common in metal parts (Figure 1). Surface preparation and coating options range from polishing and blasting to pickling, passivating and plating. Application of the coating adds another layer of complexity to the finishing process. So, how do you know if your coating is going to hold up over time and exposure to the elements before going into production? The answer is simple: environmental simulation and/or accelerated corrosion testing. Corrosion Costs to America The products of corrosion that are at times an aesthetic annoyance cannot be compared to the potential of failure to many corrosion modes. The numerous hidden costs of corrosion structures, equipment, bridges, proactive coatings, specialty materials, cathodes, anodes, and other manufactured parts are just some of the items that suffer the effects of corrosion. The coatings industry is experiencing pressure from environmentalist groups, corporate sustainability programs and individuals to produce "greener" products. Environmentally friendlier coatings usually have less corrosion resistance over the lifetime of the coating or finish. This had left the industry, in some situations, struggling to come up with new alternative formulations that perform as well as their less environmentally friendly counterparts. The price of corrosion is staggering. Some quick costs for corrosion include $108 billion in protective coatings, $7.7 billion for Corrosion Resistant Alloys (CRA), and $1.1 billion spent on corrosion inhibitors, to name a few. The total direct cost of corrosion in America is $276 billion in 2012. To emphasize how large this number is in 2012, it is projected to be 3.1% of the United States GDP. Cabinet Salt Spray and Humidity Testing Tests such as neutral salt spray testing (NSS) and humidity testing can help a Figure 1 (left): Painted power transfer assembly prior to exposure to neutral salt spray (NSS). Figure 1a (right): Salt spray exposure IAW ASTM B117-11 in process. 513

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