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Corroded steel support friction joint load capacity studies as found in Piast-Ziemowit coal mine This article presents the load capacity study results of the corroded friction joints obtained during heading relining conduction. The main goal of the study was to determine the operational characteristics of heavily corroded friction joints as well as their load capacity. An additional goal of the study was to indicate which parameter is crucial from the point of view of corroded support technical condition evaluation-friction joint load capacity or arch strength. Mine conditions in which the LP support operated were also briefly characterized in the article. The study presented in the article is of a pilot character; while the obtained results reveal a very significant influence of corrosion on the support operational safety, the studies of corroded joints will be continued in the future using a larger number of samples and various types of shackles.

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A new electrochemical test for predicting the stress corrosion performance of 2219 alloy products in the T851 and T87 tempers is described. The test requires only a simple measurement of solution potential of an unstressed specimen in a mixture of absolute methyl alcohol and carbon tetrachloride. It is rapid, requiring less than an hour and has the outstanding advantage of providing differences of nearly 200 millivolts between borderline and resistant conditions of stress corrosion susceptibility, as contrasted to differences of less than 20 millivolts in conventional NaCl-H2O2 solution. The test offers an attractive possibility for evaluating stress corrosion performance of 2219 products quickly as an alternate or supplement to the conventional 30-day alternate immersion exposure in 3½% sodium chloride solution. The mechanism of the reaction between 2219 and this organic electrolyte suggests that a similar test can be developed for other aluminum alloys.