02 Electrochemistry and Corrosion Flashcards
electrochemical cell
An _____________ is a device that can generate electrical energy from the chemical reactions occurring in it, or use the electrical energy supplied to it to facilitate chemical reactions in it. These devices are capable of converting chemical energy into electrical energy, or vice versa.
galvanic cell; electrolytic cell
A ____________ converts chemical energy into electrical energy; while ____________ electrical energy into chemical energy
loss
gain
Oxidation is ______ of e-
Reduction is ______ of e-
galvanic cell; electrolytic cell
Spontaneous redox reaction: _______________
Nonspontaneous redox reaction: _______________
water
The presence of ______________ is necessary in order to transport ions to and from the metal, but a thin film of adsorbed moisture can be sufficient.
Galvanic Corrosion
Also called “dissimilar metal corrosion” or wrongly “electrolysis”) refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte.
less; more
In a bimetallic couple, the __________ noble material becomes the anode and tends to corrode at an accelerated rate, compared with the uncoupled condition and the __________ noble material will act as the cathode in the corrosion cell
Luigi Galvani
Late 18th century- The bimetallic driving force was discovered through as series of experiments with the exposed muscles and nerves of a frog that contracted when connected to a bimetallic conductor.
Alessandro Volta
1800- the principle was later put into a practical application by first electrical cell, or battery: a series of metal disks of two kinds, separated by cardboard disks soaked with acid or salt solutions.
Sir Humphry Davy
Early 19th century- The principle was also engineered into the useful protection of metallic structures.
Electrolyte
A conductive solution, like saltwater or even tap water, that allows the flow of ions between the anode and cathode.
Electrical connection
A metallic pathway connecting the anode and cathode, allowing the flow of electrons to complete the circuit.
anode; cathode
Less noble: _____________; more noble: _____________.
sacrificial anode
Introducing a more active metal, called a ________________, can be strategically placed to corrode preferentially and protect the desired metal. This principle is used in cathodic protection systems for pipelines and other structures.
coatings
Applying protective _____________ to the anode can create a barrier and impede its interaction with the electrolyte.
Electrode Potential
It is the tendency for an electrode to lose or gain electrons when dipped in the solution of its ions.
1 atm; 298 K; 1 M
Standard Electrode Potential is measured at _____ atm, _____ K, and _____ M.
two
Zinc atoms in the rod undergo oxidation by losing _____ electrons to form zinc ions which go into the solution
-0.76
The reduction potential of zinc electrode is ____________, which implies that ZINC is more electropositive than hydrogen
0.34
The reduction potential of zinc electrode is ____________, which implies that COPPER is more electropositive than hydrogen
anode to cathode
Electrons always flow from __________ to __________.
Current
_____________ is produced in an electrochemical cell while corrosion is occurring.
Electrochemical corrosion
_______________ involves the transfer of electrons from the anode to the cathode.
Corrosion rate
This is the speed at which any given metal deteriorates in a specific environment.
instantaneous
Electrochemical corrosion rate is “________________.”
number of coulombs
Faraday developed the ________________ known as “FARADAY”
Faraday’s First Law of Electrolysis
This law states that: Amount of substance produced at each electrode is directly proportional to the charge flowing through the cell.
electro-chemical equivalent
In Faraday’s First Law of Electrolysis, z is a constant, and known as ______________, and is characteristic of the substance deposited.
Mass of Oxidized Metal
This is the formula for _________________ under Faraday’s First Law of Electrolysis.
Corrosion Rate
This is the formula for _________________ under Faraday’s First Law of Electrolysis.
Electrochemical Process
It is defined as a chemical reaction involving the transfer of electrons between two electrodes in an electrochemical cell.
Luigi Galvani
The galvanic cell is named after _____________, a physician in Bologna, Italy, who published his studies of electrochemical action in 1791.
electrochemical cells
It is a device that converts chemical energy produced in a redox reaction into electrical energy
half-cells
Electrochemical cell is composed of two compartments or _______________, each composed of an electrode dipped in a solution of electrolyte.
positive to negative
On short-circuiting such a cell (attaching a low - resistance wire to connect the two electrodes), positive current flows through the metallic path from ___________ electrode to ___________ electrode.
negative to positive
Electrons, of course, go from ___________ to ___________ pole, opposite to the imaginary flow of positive carriers.
Anode
Denoted by a negative sign that releases electrons to the external circuit and oxidizes during an electrochemical reaction.
Cathode
Denoted by a positive sign that acquires electrons from the external circuit and is reduced during the electrochemical reaction.
Salt Bridge
It is a device used in an electrochemical cell for connecting its oxidation and reduction half cells wherein an inert electrolyte is used. It is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution.
Electrolytes
It is the medium that provides the ion transport mechanism between the cathode and anode of a cell. They are often thought of as liquids, such as water or other solvents, with dissolved salts, acids, or alkalis that are required for ionic conduction.
Standard Reduction Potential
It lists elements and compounds in terms of how strongly they desire to pull electrons, therefore the higher you go up here, the more these elements want to attract electrons towards them.
electrochemical cell
It is a container in which chemical reactions produce electricity, or an electric current produces chemical change.
electrolytic cell
Use electricity to force electrons to move between atoms to make oxidation-reduction reactions happen
electrochemical cell;
electrolytic cell
ΔG < 0: _______________
ΔG ≥ 0: _______________
Dissimilar Electrode Cell
These cells involve different types of metals or metal compositions coming into contact, leading to electron transfer between them.
Salt concentration cell
These are cells with two identical electrodes, each in contact with a solution of different composition.
Differential Aeration Cell
Part of the metal exposed to air is more oxygenated and acts as a Cathode. Part of the metal immersed in the electrolyte is poorly oxygenated & acts as an anode.
Differential Temperature Cell
This is the type of cell when two identical electrodes are immersed in same electrolyte, but the electrodes are immersed into solution of two different temperatures.
emf Series
The __________ is an orderly arrangement of the standard potentials for all metals. The more negative values correspond to the more reactive metals.
Galvanic Cell
It arises when two metals with dissimilar compositions come into contact in the presence of an electrolyte.
Galvanic Series
Determines the electrochemical potential and nobility of metals (and metal alloys). Ranking of metals and alloys according to their free corrosion potential in a given electrolyte.
Voltmeter
Used to measure potential differences.
platinum
The reaction of SHE generally takes place on a ___________ electrode.
Calomel Reference Electrode
Pure mercury is placed at the bottom of the tube, which is covered with a paste of mercury- mercurous chloride (Hg+ Hg2Cl2).
Silver-Silver Chloride Reference Electrode
Composed of a silver wire, sometimes coated with a layer of solid silver chloride, immersed in a solution that is saturated with potassium chloride and silver chloride.
Saturated Copper-Copper Sulfate Reference Electrode
Consists of metallic copper immersed in saturated copper sulfate. It is used primarily in field measurements where the electrode must be resistant to shock and where its usual large size minimizes polarization errors.
Faraday’s empirical laws of electrolysis
These relate the current of an electrochemical reaction to the number of moles of the element being reacted and the number of moles of electrons involved.
96,485 C/mol of electrons
1 Faraday is equal to:
F∆Nn
Faraday’s Law can be expressed as:
electric current
This is an equation for charge Q that is defined in terms of ____________.
Corrosion current
It is the current produced in an electrochemical cell during corrosion. It is the dissolution current at the corrosion potential.
Corrosion rate
It is the speed at which any given metal deteriorates or corrodes in a specific environment.
Faraday’s Law of Electrolysis
Corrosion current can be converted to a corrosion rate using ______________.
Surface Area Effect
The absolute equality between the anodic and cathodic currents expressed below does not mean that the current densities for these currents are equal.
amplifying factor
stifling factor
If Sc/Sa is»_space; 1, _____________
If Sc/Sa is «_space;1, _____________
Resistance control
This occurs when the electrolyte resistance is so high that the resultant current is not sufficient to appreciably polarize anodes or cathodes.
corrosion current
The _____________ can be calculated from the corrosion potential and the thermodynamic potential.
Stern-Geary approximation
This equation is known as:
real polarization plots
The Tafel slopes in
Theory of Cathodic Protection
Impressed current cathodic protection (ICCP) or by another metal that corrodes more readily than the metal being protected and therefore is sacrificed is the process.
zero
If the metal is polarized slightly beyond the open -circuit potential, φA , of the anode, the corrosion rate remains ___________.
degree of protection
Should the applied current fall below that required for complete protection, some ______________ occurs.
This is associated with the activation energy required to initiate the electrochemical reaction at the electrode surface. It represents the energy barrier that must be overcome for the reaction to proceed.
Activation Polarization
____________ activation overpotential can contribute to increased corrosion resistance by reducing the rate at which the metal reacts with the corrosive environment.
High
Activation polarization is due to ______________ that are an inherent part of the kinetics of all electrochemical reactions.
retarding factors
The __________________ is the single most important variable that explains the large differences in the rate of hydrogen production on metallic surfaces. It is influenced by factors such as the nature of the reactants, the specific electrochemical system, and the presence of catalysts.
exchange current density
________________ is often added to power cells such as the popular alkaline primary cells to stifle the thermodynamically favored production of gaseous hydrogen and prevent unpleasant incidents.
Mercury
______________ batteries (car batteries) can provide power in a highly acidic environment in a relatively safe manner unless excessive charging currents are used.
Lead acid
This type of overpotential arises from the variation in ion concentrations at the electrode interface.
Concentration polarization
When a chemical species participating in a corrosion process is in short supply, the mass transfer of that species to the corroding surface can become __________________.
rate controlling
Mass transport to a surface is governed by three forces, that is, _____________, _____________, and _____________.
diffusion, migration, and convection
In mass transport, the ______________ term is negligible since it only affects charged ionic species while the ______________ force disappears in stagnant conditions.
migration; convection
The flux of a species O to a surface from the bulk is described with _______________.
Fick’s first law
