TABLE OF CONTENTS The compositions of body fluids are complicated. However, from the corrosion perspective, the most important characteristics are the chloride, dissolved oxygen and pH levels. A 0.9% NaCl solution is considered to be isotonic with blood, and under normal conditions most body fluids have a pH of 7.4 and a temperature of 37 C. In these respects, body fluids appear to be slightly less aggressive than seawater. This is reflected by the fact that for stainless steels, a pitting resistance number (PREN) of greater than 26 is recommended for surgical implants as compared to the value of 40 usually required for stagnant seawater [23]. However, the dissolved oxygen levels in blood are lower than those of saline solutions exposed to air atmospheres, by a factor of about 2 for arterial blood and 6 for venous blood. Conversely, bicarbonate levels are about 20 times higher in blood than in seawater [53].
The many other components in body fluids, e.g., phosphates, cholesterols, phospholipids, etc. are usually thought to either play no role in the corrosion process or exist at inconsequential levels. As a result most in vitro experiments have been conducted in either 0.9% NaCl solution or standard isotonic solutions (such as Ringer s or Hank s solution) in which the presence of bicarbonate and calcium chloride poses as the main difference from the NaCl solution. A review by Solar [76] in 1979 concluded that inorganic solutions based on diluted NaCl were indeed satisfactory substitutes...
