wht are the practical significance of these effects, e.g. the corrosion resistance of stainless steels under different conditions.

Corrosion of Stainless Steel The resistance to corrosion of stainless steel is due to a thin air-tight film of chromium oxide. However, if this film is destroyed the electromotive potential is about the same as that of iron and its corrosive resistance is correspondingly the same. The presence of an 13 adherent film indicates a passive condition whereas destruction of the film leads to an active state. Clean an ordinary steel plate for about 2 minutes in 10%HCl and rinse in water. Passify 2 pieces of stainless steel in prepared dilute nitric acid for about two minutes, then rinse with water. Fill a 250ml beaker with about 200ml5%H2SO4 Clamp one stainless steel plate and the ordinary steel plate as seen in Figure 3.1 and connect the voltmeter leads. Use the 0 - 2 volt range. Lower the assembly into the beaker and observe and record the potential. Now bring the two electrodes into contact. During contact and upon separation of the electrodes, record the potential. Repeat the procedure several times recording the potentials upon contact and upon separation. Replace the ordinary steel electrode with the second stainless steel strip (passivated) and observe and record the potential. (If negative, reverse the leads and record the potential.) Explain the changes in potential for each case. Explain the practical significance of these effects, e.g. the corrosion resistance of stainless steels under different conditions