Carnegie Scholarship Memoirs Volume 11

Carnegie Scholarship Memoirs Volume 11

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ...when cast iron negative to wrought iron...----0-006---0-003 Greatest potential difierence observed whilst cast iron negative....--0-011---0-005 Total number of days in which cast iron negative...... 66 53 A consideration of the foregoing results reveals the interesting fact that not only does the potential difference between the metals vary, but it may actually become reversed. Thus, for 233 days cast iron I. was at a higher potential, and hence less corrodible than wrought iron, whilst for 66 days it was at a lower potential, and hence more corrodible than the wrought metal. The total relative corrosion during the period is the sum of these two efiects. The polarity changed but once. Andrews found, however, in the case of hard Bessemer steel when connected with wrought iron, no fewer than sixteen reversals or interchanges of polarity during 300 days. When inquiry is made into the cause of these reversals, the problem is found to be very complex. The surface condition is mainly responsible for the electrical condition, and any protective, non-corrodible skin will tend to raise the potential and reduce corrosion. In neutral corroding media the rust usually adheres to some extent to the metal, and markedly influences the potential difierence. Finally, as the metal corrodes away, fresh surfaces become attacked, and if these vary slightly in composition or in physical condition, the potential difference must be proportionately affected. Hence with those metals where the initial potential difference is but small, as in the case of ordinary wrought iron and steel, reversals will the more easily occur. In 1885 Andrews1 published further data. Having prepared series of plates of wrought and cast irons of the dimensions shown in Fig. 4, and having...show more

Product details

  • Paperback | 44 pages
  • 189 x 246 x 2mm | 95g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236844645
  • 9781236844644