# Experiment 4: Corrosion


Background
Corrosion reactions are redox reactions in which a metal is attacked by some substance in its environment and converted to an unwanted compound. Corrosion cuts short the lifetimes of steel products such as bridges and automobiles, and replacing corroded metal parts cost billions of dollars a year: about 20 percent of the iron produced annually in this country is used to replace iron objects that have been discarded because of rust damage. Rusting of iron is known to require oxygen and water. The rusting process is summarized in the following figure (figure II.4.1):

Materials:

Solution A: contains $$K_3[Fe(CN)_6]$$, $$NaCl$$, and phenolphthalein.
Iron metal plate
Scotch Brite pad to clean metals

Procedures:

• Clean one of the surfaces of the iron plate with Scotch Brite.
• Place a drop of Solution A.
• Set aside and record your observations.

Clean-up: Rinse the iron plate under running water.

Discussion:

• Draw a scheme showing your observations.
• Write the balanced chemical equations for all processes. Identify the colored species.
• What are the oxidized and reduced species? Identify the anode and the cathode reactions.
• What's the function of the hexacyanoferrate(III), NaCl, and phenolphthalein?
• How can corrosion be avoided?

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