Teflon Coated Brush Holders for Pickling Line
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In the steel industry, pickling operations are used to remove surface oxides and clean rust or scale buildup. These operations are very important for the manufacture of steel, but they are notorious for their corrosive atmosphere.
A pickling operation environment can cause premature failure of brass brush holders if they are not properly protected. This corrosive atmosphere can cause the brass brush holder to degrade, and the carbon brush can seize in the holder, which could result in flashover and significant damage to the motor, generator, and slip rings.
The most common solution used to treat carbon steel products contains either hydrochloric (HCI) or sulfuric acid (H2SO4), which can bring challenges dues to its corrosiveness. This harsh environment creates concern surrounding the DC motors and generators used throughout the steel mill and pickling line. Some steel mills report the need to replace brushes and holders every month due to corrosion and oxidation, mainly from issues caused by restricted brush movement in the holder. Effective sliding electrical contact requires free movement of the carbon brushes in the holder.
Helwig Carbon Products decided to test several potential solutions to brush holder degradation in this harsh environment. Three different coatings were applied to brush holders and tested in a containment chamber while exposed to circulating HCI fumes for 40 hours. The coatings tested were Teflon™, Nickel, and a Duplex coating of Silver over Copper. The effectiveness of the corrosion protective coating can be determined by comparing the images of the brush holders before and after the test.
The testing conducted demonstrated the importance of using the proper brush holder coating to protect the brass brush holders from corrosion in an acid fume environment. The unprotected brush holder showed extensive corrosion during the test and the carbon brush was seized in the holder at the end of the test. This would have led to a failure in an actual steel mill application. Similarly, the nickel-plating holder showed extensive corrosion and the brush was seized in the holder. The copper-silver duplex coating has minimal corrosion during the test, but the brush was seized in the holder.
The brush holder with Teflon™ coating protected the brass brush holder and allowed the brush to move freely. Teflon™ coating is the most effective corrosion preventative coating for brass holders in an HCI environment like the pickling lines in steel mills. Helwig Carbon products recommends the use of Teflon™ coated brush holders to provide maximum service life and reduced downtime for the DC motors used in this harsh environment. Several popular models are in stock and retrofit designs can be quickly created.
Helwig Carbon Products, Inc. is the premier, family-owned American manufacturer of carbon brushes, brush holders, spring assemblies, Bearing Protection Kits™, metal graphite brushes, and mechanical carbons. Since 1928, we have forged innovations that have since become industry standards and requirements. We pride ourselves on manufacturing all of our products to the highest standard and performance because we know your application depends on it!