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An in-depth exploration of the electrochemical process of corrosion, including the flow of protons, electrons, and ions, as well as the four key components of a corrosion cell. It delves into the concepts of polarization, passivity, and the factors that affect them, such as temperature and metal ion concentration. The document also covers the principles of cathodic protection, including the use of anodes, rectifiers, and other components, as well as methods for detecting and monitoring corrosion, such as dcvg surveys and four-wire testing. The information presented in this document is highly relevant for students and professionals in fields related to materials science, electrochemistry, and corrosion engineering.
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NACE 2008 Student Manual! START OF CHAPTER 1 Corrosion is an electrochemical process involving A) flow of protons and electrons B) flow of neutrons and ions C) flow of protons and ions D) flow of electrons and ions E) flow of resistance and resistivity - ANSWER>>>d Metal loss or corrosion occurs at the A) cathode B) anode C) electronic path D) metallic path - ANSWER>>>b What are the four parts of the corrosion cell
A) anode, resistor, electrolyte, metallic path B) anode, cathode, electron, electronic path C) anode, cathode, electrolyte, metallic path - ANSWER>>>c True or False (t or f): Ions exist only in the electrolyte? - ANSWER>>>t Electrons flow in a corrosion cell by which of the following paths? A) anode to cathode via electrolyte B) cathode to anode via electronic path C) anode to cathode via electronic path - ANSWER>>>c At the cathodic surface in a corrosion cell, the electrons from the ____ meet ____ ions from the solution. A) cathode, hydrogen B) cathode, OH- C) anode, hydrogen D) anode, OH- - ANSWER>>>c Oxidation of the metal occurs at the ____ surfaces and reduction of ____ ions occurs at the ____. A) anodic, hydrogen, cathodes B) cathode, OH-, anodic C) anodic, OH-, cathodes D) cathode, anodic, electrolyte E) cathode, hydrogen, electrolyte - ANSWER>>>a True or false Is oxidation necessarily associated with oxygen? - ANSWER>>>f Current flow in a corrosion cell flows which path:
A) ores B) anodic metals C) cathodic metals D) carbohydrates - ANSWER>>>a The amount of energy required by a metal during the refining process determines the ___ or _______ of the metal. A) current, active state B) voltage, active state C) active resistance, voltage D) resistance, active state E) current, active resistance - ANSWER>>>b During the refining stage of metal the ____ the energy, the more ____ the metal and the more tendency it has to corrode. A) higher, inactive B) lower, active C) higher, active D) lower, inactive - ANSWER>>>c What is the most common iron ore? A) hemophite B) hematite C) magnesium D) calcium E) aluminum - ANSWER>>>b True or false
Iron is considered thermodynamically unstable? - ANSWER>>>t True or false Gold is more noble than zinc? - ANSWER>>>t Which of the following metals is most active? A) magnesium B) copper C) iron D) nickel E) platinum - ANSWER>>>a Electromotive force (emf), is ____ in sign and magnitude to the electrode potential of the ___ less the electrode potential of the ____. A) unequal, cathode, anode B) unequal, anode, cathode C) equal, cathode, anode D) equal, anode, cathode - ANSWER>>>d The driving force for electrochemical corrosion is ____ A) current B) voltage C) resistance D) ohms E) siemens-cm - ANSWER>>>b In relation to a corrosion cell, ____ is the net transfer of electric charge per unit time A) current
What is the potential of zinc in a 0.01 molar zinc chloride solution at 25C? A) - 0.892V B) - 0.287V C) - 0.827V D) - 0.297V E) - 0.889V - ANSWER>>>c E= - 0.763 + (0.059/2) * log (0.71 *0.01/1) = - 0.827V Standard conditions for pure metals in the emf series are based on one unit activity of metal ions in the electrolyte at ___ C with no impurities in the metal or electrolyte and with reference to a standard ____ electrode. A) 25, hydrogen B) 35, hydrogen C) 25, CSE D) 35, CSE E) 25, SSC F) 35, SSC - ANSWER>>>a The ____ the concentration of metal ions in the electrolyte, the ____ the metal. A) lower, less active
B) higher, less active C) lower, more active D) higher, less active - ANSWER>>>b In reference to the temperature in a corrosion cell, in most cases, electrode at the _____ temperature becomes the ____ A) lower, anode B) higher, cathode C) lower, cathode D) higher, anode - ANSWER>>>d During metal fabrication of structures, highly stressed areas of a metal will tend to be at ____ energy levels, thus more ____ than less stressed areas A) higher, active B) lower, active C) higher, inactive D) lower, inactive - ANSWER>>>a True or False (t or f): Corrosion cells may form because of differences in the electrolyte - ANSWER>>>t ____ cells are responsible for much of the corrosion that take place in soils, particularly in bare or poorly coated pipe A) concentration B) steady state C) carbon D) dynamic E) telluric - ANSWER>>>a In many cases in naturally occurring soils, a portion of pipe lying in the more _____ soil is the ____ and in the less ____soil is the ___.
C) cathode is the metal under the pavement, the anode is the metal outside the pavement - ANSWER>>>b In a metal ion concentration cell, the surface in contact with ____ concentration of metal ions acts as the
A) lower, anode B) lower, cathode C) higher, anode D) higher cathode - ANSWER>>>a Theoretically, the potential of a structure changes by about ____mV for each pH unit A) 40 B) 50 C) 20 D) 70 E) 60 - ANSWER>>>e The corrosion potential of a metal might be - 500mV in an environment with a pH of 7, but the corrosion potential might be ____ at a pH of 8? A) - 440mV B) - 660mV C) - 300mV D) - 560mV - ANSWER>>>d True or false (t or f) an acidic pH can be harmful to concrete, such as reinforced concrete structures? - ANSWER>>>t A pH of less than ____ is considered to be harmful to concrete? A) 4 B) 6
E) 8 - ANSWER>>>c The rate of corrosion is directly ____ to ____ flow? A) inproporinate, current B) inproporinate, voltage C) proportional, voltage D) proportional, current - ANSWER>>>d If a 1 Amp CP system must last 40 years and the electrochemical equivalent for silicon chromium cast iron anodes is 0.75 lb/A-yr, how many pounds of anodes are needed? A) 50lbs B) 35lbs C) 25 lbs D) 45lbs E) 30lbs - ANSWER>>>e All things being equal, the greater the magnitude of the difference between two voltages of metals, the ____ the current flow and rate of corrosion A) higher B) lower - ANSWER>>>a True or False ( t or f) Magnesium will corrode at a slower rate when connected to steel rather than zinc? - ANSWER>>>f Which reference electrode is considered a primary reference electrode because it is used to determine the potential of other secondary reference electrodes that are better suited for field use? A) CSE B) Ag/AgCI
Which of the following is primarily a laboratory electrode? A) CSE B) Ag/AgCI C) Calomel D) Zinc - ANSWER>>>c When doing a structure to electrolyte potential , the structure is connected via the _____ terminal and the reference is connected via the _____ terminal A) negative , positive B) positive, negative - ANSWER>>>b A potential of - 0.810Vcse converted to Calomel (SCE) A) +0.306 sce B) - 0.750 sce C) - 0.735 sce - ANSWER>>>c A potential of - 0.810Vcse converted to Ag/AgCI (SSC) A) +0.306 ssc B) - 0.735 ssc C) - 0.750 ssc - ANSWER>>>c A potential of - 0.810Vcse converted to Zinc (ZRE) A) +0.306 zre B) - 0.735 zre C) - 0.750 zre - ANSWER>>>a True or False (t or f)
The potential of a STATIONARY reference electrode should be checked from time to time with a portable reference electrode that is known to be accurate under "no current" conditions. - ANSWER>>>t As current is impressed on a metal over time, where does polarization occur? A) at the anode and the cathode B) at the anode C) at the cathode - ANSWER>>>a Polarization _____ the potential difference between the anode and the cathode and by Ohm's Law, the current ___ and the corrosion rate ____ until an equilibrium is reached A) lowers, drops, decreases B) increases, increases, decreases C) lowers, increases, decreases D) lowers, drops, decreases - ANSWER>>>d Depolarizers include: I dissolved oxygen II microbiological activity III water flow A) only I B) only II C) I and II D) I, II , III - ANSWER>>>d The name for the current that exists during the steady state of polarization is called the _____ of the system A) telluric current
D) reactant polarization - ANSWER>>>a _______ is the result of reaction steps involving the diffusion of reactants up to the reaction products away from the reaction surface A) activation polarization B) concentration polarization C) mixed polarization D) reactant polarization - ANSWER>>>b Anything that causes a depletion of available reactants or a buildup of reaction products results in a ____ in the reaction rate and an _____ in concentration polarization. A) decrease, increase B) increase, decrease - ANSWER>>>a If the slowest step in the overall process involves waiting for arrival of reactants or the removal of reaction products, the reaction is under __________ control. A) activation polarization B) concentration polarization - ANSWER>>>b If the slowest step in the overall reaction process is is on the metal surface or in the charge transfer reaction the process is under _____ A) activation polarization B) concentration polarization - ANSWER>>>a __________ usually predominates in electrolytes where the concentration of the reactants is low, as with dilute solutions, or there is a buildup of reaction products from activation polarization or in stagnant environments.
A) activation polarization B) concentration polarization - ANSWER>>>b As polarization ____ , current _____ A) increases, decreases B) decreases, decreases C) increases, increases D) decreases, increases - ANSWER>>>c An increase in ions will result in a ____ in resistivity A) increase B) decrease - ANSWER>>>b The effect of current concentrated on a small area will be ____ than the effect of the same amount of current on a ____ area. A coated structure will polarize more rapidly than a bare structure A) larger, larger B) less, larger C) greater, smaller D) smaller, smaller E) greater, larger - ANSWER>>>e True or False (t or f) A small anode and a large cathode is desirable - ANSWER>>>f A(n) ____ in temperature has a tendency to ____ chemical reactions, which _____ the electrodes and _____ current A) increase, increase, depolarizes, increases B) increase, increase, depolarizes, decrease
D) oxygen, hydrogen - ANSWER>>>d In regards to cathodic reactants, a(n) _____ in the concentration of either of the reactants of oxygen or hydrogen will _____ polarization of the cathode and _____ current and vice versa A) increase, decrease, decrease B) decrease, decrease, decrease C) increase, decrease, increase D) increase, increase, decrease E) decrease, decrease, increase - ANSWER>>>c Passivity can be defined as the A) gain of chemical reactivity B) polarization of chemical reactivity C) loss of chemical reactivity D) depolarization of molecular reactivity E) polarization of molecular reactivity - ANSWER>>>c The ____ region is when a slight increase in corrosion potential causes the corrosion current to increase A) transpassive B) passive C) nonpassive D) active - ANSWER>>>d The ____ region is when the corrosion potential increases to a certain point, however, the corrosion current suddenly decreases and remain essentially constant A) transpassive B) passive C) nonpassive
D) active - ANSWER>>>b The ____ region occurs if the potential is increased sufficiently thus current again increases A) transpassive B) passive C) nonpassive D) active - ANSWER>>>a For the active (or nonpassivating) metal, as corrosion potential _____, corrosion current ____, more or less logarithmically (or linearly on a semi- log graph). A) increases, increases B) decreases, decreases C) increases, decreases D) decreases, increases - ANSWER>>>a This type of film which forms naturally on most metals when they are exposed to the air, can provide substantial protection against further attack by many environments A) ore B) oxide C) reductant D) selimum - ANSWER>>>b Type of corrosion with an even loss of metal over the entire area or a large area of the structure A) Galvanic attack B) intergranular attack C) selective leaching D) velocity phenomena E) pitting
