Explain the following observations, using diagrams to illustrateyour answer wherever possible:
(a) Steel nails used to hold copper roofing sheet in positionfailed rapidly by wet corrosion.
(b) The corrosion of an underground steel pipeline was greatlyreduced when the pipeline was connected to a buried bar ofmagnesium alloy.
(c) Mild-steel radiators in a central heating system were foundto have undergone little corrosion after several years'service.
(d) A reaction vessel for a chemical plant was fabricated bywelding together stainless steel plates containing 18% chromium, 8%nickel and 0.1% carbon. During service, it was observed that thevessel corroded badly near the welds.
