Ib Design Lab

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Corrosion of Metals

Chemistry 30 IB - 5
Pre-Lab Information
Rusting of metals is a form of metal oxidation. Iron will oxidize to for rust, water causes metal to rust, and by adding a salt, the oxidation can be accelerated. In steel (>99% Iron) the metal corrodes as such: Fe -> Fe+2+2e-

The electrons removed from iron will then be consumed by undergoing a reduction reaction with anther substance: O2+4e+2H2O->4OH-

This means what in order for rust to occur, an oxidation reduction reaction has to happen, in which metal becomes metal ions and oxygen and water becomes hydroxide ions. For this reaction to occur the electrons must be transported from the metal to where oxygen is consumed and an ionic current must also flow between the sites to complete the circuit. This would mean rust occurs much quicker in a salty environment.

Phenolphthalein turns pink in the presence of hydroxide, and iron cyanide turns blue in the presence of iron II++, or rust. This can be used to determine whether an oxidation or reduction reaction has occurred.

Corrosion of steel may be slowed down by coatings which protect the metal from corrosive environments. Many examples of this can be found in food cans which use polymer coatings, etc protect the can.

Purpose
The purpose of this investigation is to observe and record the corrosive nature of oxidation-reduction reactions and determine the relative strengths of oxidizing and reducing agents. Problem
What can be done to reduce or prevent the effects of corrosion on steel? Hypothesis
If we add a coating to the metal, then the coating will be protecting the metal from the corrosive environment. Design
In this experiment, we watch the corrosion reaction by using substances that causes a color change when they react with the products of ion being oxidized or oxygen undergoing reduction. Phenolphthalein turns pink in the presence of hydroxide, and iron cyanide turns blue in the presence of iron II++, or rust. The...
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