Concept explainers
A galvanized (zinc-coaled) steel sheet is found to uniformly corrode at the rate of 12.5 × 10-3 mm/year. What is the average current density associated with the corrosion of this material?
The average current density associated with the corrosion of zinc coated steel (galvanized steel).
Answer to Problem 55AAP
The average current density associated with the corrosion of zinc coated steel (galvanized steel) is
Explanation of Solution
Write the expression for corrosion rate.
Here, the corrosion rate is
The current density is expressed as,
Substitute
Write the formula to calculate the corrosion rate per area.
Here, the corrosion mass is
Conclusion:
It is given that the corrosion depth rate is
Convert the unit
The density of the zinc is
Substitute
Equation (III).
Refer Table 13.1, “Standard electrode potentials at 25 °C”.
The anodic reaction of iron is as follows:
Here, the number of electrons produced is,
Refer Figure 2.3, “Periodic Table of Elements”
The atomic mass of zinc is,
Substitute
Thus, the average current density associated with the corrosion of zinc coated steel (galvanized steel) is
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Chapter 13 Solutions
Foundations of Materials Science and Engineering
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