____________ [Chemistry 3] Experiment No 3.1
K. M. U. AMANDORON, R. N. T. COLANAG, E. J. G. MERIN, F. T. OPADA, R. J. C. PARBA
Philippine Science High School - Central Visayas Campus
Talaytay, Argao, Cebu, Philippines
Date performed: December _, 2013
Date submitted: January 6, 2013
Corrosion is a process through which metals in manufactured states return to their natural oxidation states, a reduction-oxidation reaction in which the metal is being oxidized by its surroundings, often the oxygen in air . The first part of the experiment involved the products of rusting. Certain amounts of 3% NaCl, 10% K3Fe(CN)6 and ...view middle of the document...
For the copper wire – iron nail combination, it was concluded that the iron nail “rusts” while the copper didn’t react with anything, so the copper wire was the cathode site while the iron nail was the anode site. In bimetallic corrosion, corrosion of a metal is accelerated when placed in contact with metal with a different and higher potential. The metal which oxidizes easily and is the anode will be the one that will corrode.
Corrosion is usually defined as degradation of the properties of a material as a result of chemical reaction with the environment.  Corrosion is a spontaneous electrochemical process that has caused tens of billions of dollars of damage to cars, ships, buildings, and bridges each year. The most common and economically destructive form of corrosion is the rusting of iron. Rust is not a direct product of the reaction between iron and oxygen but arises through a complex electrochemical process. 
There were two parts of the experiment. The first one involved the products of rusting. 15 mL of 3% NaCl, 4 drops of 10% K3Fe(CN)6 and 2 drops of phenolphthalein were combined in a small beaker. In this mixture, a piece of plain white paper napkin was folded and was soaked. After soaking, two nails (one straight, one bent) were wrapped in the folded damp paper allowing space between them. This setup was left for 10 minutes. After which, colors formed in the paper napkins were observed. The second part of the experiment was the bimetallic corrosion. Two iron nails were cleaned using sand paper. In one iron nail, copper wire was coiled around its tip. On the other iron nail, a zinc granule was attached to its tip. Another plain white paper was folded and was soaked in the mixture with 3% NaCl, 10% K3Fe(CN)6 and phenolphthalein. The iron nail with a zinc granule attached to its tip and the iron nail with the coiled copper wire were wrapped separately in the soaked folded paper napkins and were for 10 minutes. Again, the folded papers were opened and sites where pink and blue colors formed were examined. This experiment aims to infer the products of rusting, determine anodes and cathodes of different iron nail setups and to be able to make a general statement about bimetallic corrosion.
RESULTS AND DISCUSSIONS
After leaving the first setup for 10 minutes, pink and blue-green colors appeared on the paper as seen in Figures 1 and 2.
Figure 1. Parts of the iron nails where the color pink appeared
Figure 2. Parts of the iron nails where the color pink appeared
Corrosion usually happens in a location where the metal is under stress (at a bend or weld) or is isolated from the air. The metal ions dissolve in the moisture film and the electrons migrate to another location where they are taken up by a depolarizer which in this case, is oxygen. The resulting hydroxide ions (OH-) react with the Fe2+ to form the mixture of hydrous iron oxides known as “rust” . Corrosion is actually...