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A Self-Learning Manual - Institution of Engineers Mauritius

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A <strong>Self</strong>-<strong>Learning</strong> <strong>Manual</strong><br />

Mastering Different Fields <strong>of</strong> Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU<br />

Institute (2002).<br />

17. What is the mechanism <strong>of</strong> protection by hot dip galvanizing? (S10)<br />

Hot dip galvanizing protects steel/iron from corrosion by:<br />

(i) It forms a metallic zinc and zinc-iron alloy coating on top <strong>of</strong> steel<br />

surface. This zinc coating reacts with moisture in atmosphere to from<br />

zinc salts which act as an insulating layer for steel/iron.<br />

(ii) Zinc is higher than steel/iron in the galvanic series and when these<br />

dissimilar metals with different electrical potential are in contact, the<br />

zinc anode corrodes and <strong>of</strong>fers sacrificial protection to steel/iron and<br />

hence steel/iron is protected from corrosion.<br />

400

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