Production Machining

SEP 2018

Production Machining - Your access to the precision machining industrial buyer.

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46 PRODUCTION MACHINING :: SEPTEMBER 2018 PARTS CLEANING Materials and How They are Damaged Metal rust/corrosion, discoloration, staining and weakening caused by corrosive gases Plastic strength loss and discoloration caused by ozone, ultraviolet rays and nitrogen oxides Rubber flexibility and strength losses caused by ozone, ultraviolet rays and nitrogen oxides Paint surface erosion caused by sulfur oxides, hydrogen sulfides and nitrogen oxides Fabric reduced strength and degradation caused by sulfur and nitrogen oxides Paper embrittlement, degradation and discoloration caused by sulfur oxides Leather weakening and powdery surface caused by sulfur oxides Ceramic changing surface appearance caused by acid gases Digital/ Magnetic changing surface topography caused by acid gases or erasure of data caused by electric fields C orrosion control is a goal of both machine and finishing shops. Metals are mined, refined and made into items useful in unstable environments. However, most metals eventually will revert to a more stable form, making them less than useful. Over the centuries, materials have been developed and methods implemented to slow the corrosion process, including the use of oils to coat metal surfaces. From a cost and environmental standpoint, this is not necessarily the best way. Getting a better understanding of what causes corro- sion and rust will help us develop new plans and materials to protect against this destructive metal state. Causes of Corrosion Nonferrous (non-iron) metals corrode primarily because of reactions with corrosive gases, also called "atmospheric pollution." Even ferrous metals are severely impacted by these same corrosive gases, which act as corrosion acceler- ants. Metals corrode faster near the sea because there are higher levels of chlorides in the air, which are particularly damaging to stainless steel and aluminum. In fact, looking at materials in general, the same corrosive gases that corrode and rust metals impact materials across the board. Once the main culprit of corrosion is identi- fied, the goal is to determine how to neutralize, minimize or eliminate corrosion from metals in storage. Traditionally, oils have been used to provide a physical barrier between materials and corrosive gases. However, dust, dirt and other particles in the air can contaminate these oils and, in many cases, will start to break the oils down. As the oils evaporate or dry, they leave the sludge or slurry of oxidized oils and these other contaminants behind, and this can and, in most cases, will accelerate corrosion. Pollution is a major issue all over the globe, Slowing Corrosion Through Cleaning and Packaging Contributed by Keith Donaldson but dust is also becoming a rising threat. It is being blamed for impacting snow packs in the Rocky Mountains, as well as accelerating corrosion in China and throughout Asia. For sulfur dioxide to be reactive, dust must be present in the air. Pollution is often worse inside factories, since many recirculate the air. Filters may remove particles, but not gases, and with the recirculation of air, the concentra- tion of those gases increases. So pollution must be kept from metal items. Oils and coatings have limitations and can actually accelerate the corrosion process if left on for any extended period of time, or if temperatures increase drying and oxidizing. Also, environ- mental concerns in Europe, where there are newer environ- mental regulations, push for oil-free solutions. e problem with going oil-free is that suddenly the cleanliness of the parts becomes extremely critical. Starting with Clean Parts is Essential Avoiding corrosion during storage begins with parts that are clean, dry, contamination-free and fingerprint-free. Fingerprints, in particular, can be highly corrosive, and Ensuring that metal parts are properly cleaned and packaged can produce better results than oil coating.

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