Abstract
Printing press cylinders release ink that is stored in a surface pattern of micro-indentations. The cylinder consists of a steel substrate electroplated with a layer of copper. A micro-indentation pattern is applied followed by a 10 μm top layer of electroplated chrome. This layer generally contains microcracks at a rate if 1000 cracks/2·5 cm. Chrome flaking was common during the warm summer months, leading to costly shutdowns. Corroded cylinders were examined using optical and scanning electron microscopy, energy dispersive spectroscopy, corrosion potential measurement and chemical analysis. It was found that rapid crevicing was taking place in the microcracks. At the chrome/copper interface, galvanically assisted crevicing further accelerated the flaking process. It was also found that the percentage of micro-indentations found to exhibit corrosion spots correlated well with measured corrosion potentials. Polymeric storage covers were recommended to limit atmospheric sources of moisture, oxygen, chlorides and sulphates.
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