Although Fig.1 indicates that chromium (Cr) is more active than iron (Fe), chrom

Question

Although Fig.1 indicates that chromium (Cr) is more active than iron (Fe), chrome plating is nevertheless a very effective procedure to prevent the corrosion (i.e., oxidation) of iron. Provide an explanation for a layer of chrome being able to protect iron despite being a more active metal. Galvanization is a process of protecting iron from corrosion by coating the metal with a layer of zinc. Although Zn is more active than Fe, Zn reacts with atmospheric gases to form zinc carbonate (ZnCO_3), a hard, durable substance which shields the remaining Zn and the underlying Fe. Suggest a series of reactions involving common atmospheric gases which could converted Zn into ZnCO_3. If the ZnCO_3/Zn coating of galvanized iron is broken and the underlying iron begins to corrode (i.e., oxidize), a chemical reaction intervenes and converts the corrosion products back to iron. Suggest a reaction which could account for this chemical protection of the iron.

Explanation / Answer

Ans 1. Chromium coating is done on the surfaces of iron parts to prolong the life of the object by preventing it from rusting or corrosion. Iron substances get rusted when they come in contact to air and moisture. Chromium plating on the iron prevents it from getting rusted as it forms a blockage between the iron and surroundings . The chromium metal forms a thin layer on the metal surface in chrome platings which do not wear off easily, even if it is oxidised. Due to this sacrificial property of chromium, the underlying iron gets saved from the corrosion.

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