The key difference between galvanic series and electrochemical series is that galvanic series shows the order of nobility of metals and semi-metals, whereas electrochemical series shows the order of standard electrode potentials of chemical elements.
The galvanic series and electrochemical series are two different lists which shows an arrangement of chemical elements according to their properties. Galvanic series shows the order of nobility, which is the resistance to corrosion and oxidation in moist air. Electrochemical cell, on the other hand, shows the standard electrode potentials of chemical elements in order.
CONTENTS
1. Overview and Key Difference
2. What is Galvanic Series
3. What is Electrochemical Series
4. Side by Side Comparison – Galvanic Series vs Electrochemical Series in Tabular Form
5. Summary
What is Galvanic Series?
Galvanic series is an arrangement of metals and semi-metals according to their nobility. Nobility is the resistance to corrosion and oxidation in the presence of moist air. This list includes metals, semi-metals and alloys because only these materials can undergo corrosion. The list is arranged according to the relative potentials of these materials in a specified environment. Generally, the environment that we consider is sea water.
Figure 01: Galvanic Series of Noble Metals
The principle behind the arrangement of this list is that, when we immerse two electrodes in an electrolyte and connect the electrodes to an external conductor, the less noble material experiences galvanic corrosion. Here, the electrolyte determines the rate of corrosion. The characteristics of this series are as follows:
• It indicates the relative positions of metals and alloys instead of potentials.
• The practical measurement of corrosion potential at equilibrium is the basis of arranging the series.
• According to this series, we can connect two alloys without any corrosion
However, there are some limitations to the usage of this series as well.
• Each environment requires a different galvanic series because it depends on the environment
• Moreover, the galvanic corrosion depends on the extent of polarization of metals and alloys; thus, the series may not provide enough information on galvanic corrosion.
What is Electrochemical Series?
Electrochemical series is a list of chemical elements which shows the order of standard electrode potentials of them. It provides enough information about the relative reactivity of metals in aqueous solutions under standard conditions. Another common name for this series is “activity series”. Furthermore, this series lists metals in order of decreasing the reactivity.
At the top of the series, it has alkali metals and alkaline earth metals. These are more reactive and easily undergo oxidation than the metals at the bottom. Moreover, they easily react to form compounds. These metals are thus called “active metals”.
At the bottom of the series, there are transition metals. They are relatively very stable and does not form compounds readily. Examples include copper, gold, silver, etc. Because of their low reactivity, we often use them to make coins, jewellery, etc.; we call them “noble metals”.
Moreover, this series gives the electrode potential of these chemical elements, and the list is arranged according to the standard electrode potentials. We can measure this value by taking the particular metal as the cathode and standard hydrogen electrode as the anode.
What is the Difference Between Galvanic Series and Electrochemical Series?
The key difference between galvanic series and electrochemical series is that galvanic series shows the order of nobility of metals and semi-metals, whereas electrochemical series shows the order of standard electrode potentials of chemical elements. When considering the principle of producing each list, galvanic series stems from the galvanic corrosion of metals and alloys while electrochemical series stems from the standard electrode potential relative to the standard hydrogen electrode potential.
Moreover, the position of a metal in galvanic series may vary according to the environment; however, in the electrochemical series, it has a fixed position. A further difference between galvanic series and electrochemical series is that galvanic series is suitable for practical applications while the electrochemical series is suitable for theoretical applications.
Summary – Galvanic Series vs Electrochemical Series
The key difference between galvanic series and electrochemical series is that galvanic series shows the order of nobility of metals and semi-metals, whereas electrochemical series shows the order of standard electrode potentials of chemical elements.
Reference:
1. “Electrochemical Series: Explanation and Its Applications.” Redefining Knowledge, 4 Dec. 2018, Available here.
Image Courtesy:
1. “Galvanic series noble metals” By Tugsataydin – Own work (CC BY-SA 4.0) via Commons Wikimedia