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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 a nd ions C) flow of protons and ions D) flow of electrons and ions E) flow of resistance and resistivity d Metal loss or corrosion occurs at the A) cathode B) anode C) electronic path D) metallic path 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 c True or False (t or f): Ions exist only in the electrolyte? 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 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- 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 a True or false Is oxidation necessarily associated with oxygen? f Current flow in a corrosion cell flows which path: A) anode to metallic path to cathode B) anode to electronic path to cathode C) cathode to metallic to anode D) cathode to electrolyte to anode E) anode to electrolyte to cathode Voltage is the measure of the electrochemical difference between two electrodes in an electrolyte e _____ is the measure of the electrochemical difference between two electrodes in an electrolyte A) current B) resistance C) error D) ohms E) ohms-cm F) voltage f The ________ represents the reversible work to move a unit charge from the electrode surface through the solution to the reference electrode A) current potential B) electrode potential C) resistance potential D) ohms potential E) Faraday potential b Metals occur in nature in the form of various chemical compounds referred to as ___ A) ores B) anodic metals C) cathodic metals D) carbohydrates 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 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 c What is the most common iron ore? A) hemophite B) hematite C) magnesium D) calcium E) aluminum b True or false Iron is considered thermodynamically unstable? t True or false Gold is more noble than zinc? t Which of the following metals is most active? A) magnesium B) copper C) iron D) nickel E) platinum 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 d The driving force for electrochemical corrosion is ____ A) current B) voltage C) resistance D) ohms E) siemens-cm b In relation to a corrosion cell, ____ is the net transfer of electric charge per unit time A) current B) voltage C) resistance D) ohms E) siemens-cm a If a metallic path connects two electrodes inside an electrolyte, the ____ difference will cause a ____ to flow between them A) current, voltage B) resistance, current C) resistance, voltage D) voltage, current E) current, resistance d The more useful method of organizing metals in order of their tendency to corrode is _____ A) emf series B) pgp series C) nuclear series D) electron series E) galvanic series e The ____ expresses the exact electromotive force of a cell in terms of the activities of products and reactants of the cell A) Ernest Equation B) Faraday Equation C) Ohm's Law Equation D) Nernst Equation E) Uniform Equation d Given the Nernst Equation, using the Valence of Common Metals Table, and using the partial Standard emf Series of Metals solve: 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 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 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 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 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 a True or False (t or f): Corrosion cells may form because of differences in the electrolyte 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 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 ___. A) inductive, anode / inductive, cathode B) inductive, cathode / inductive, anode C) conductive, anode / conductive, cathode D) conductive, cathode /conductive, anode c The two most common types of concentration cells involved in promoting corrosion are ____ and ____. A) oxygen, nonmettalic ion B) oxygen, calcium C) lack of oxygen, metal ion D) oxygen, metal ion d What is the most common of the cathodic depolarizers, that can maintain and promote a cathodic reaction? A) CO2 B) oxygen C) carbon D) OH- E) Hydrogen b Most corrosion on pipelines is on the ____ portion of the pipe A) sides B) top C) bottom c If a pipe is running through a section of pavement and through a section of non pavement: A) anode is the metal outside the pavement, the cathode is the metal under the pavement B) anode is the metal under the pavement, the cathode is the metal outside the pavement C) cathode is the metal under the pavement, the anode is the metal outside the pavement 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 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 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 d True or false (t or f) an acidic pH can be harmful to concrete, such as reinforced concrete structures? t A pH of less than ____ is considered to be harmful to concrete? A) 4 B) 6 C) 5 D) 2 E) 8 c The rate of corrosion is directly ____ to ____ flow? A) inproporinate, current B) inproporinate, voltage C) proportional, voltage D) proportional, current 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 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 a True or False ( t or f) Magnesium will corrode at a slower rate when connected to steel rather than zinc? 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 C) Calomel D) Zinc E) SHE e Most common used reference electrode for measuring potentials of underground structures? A) CSE B) Ag/AgCI C) Calomel D) Zinc E) SHE a True or false (t or f) The potential of a reference electrode in the sun can decrease from 10 to 50mV versus an electrode kept in the dark? t Which reference electrode is mostly commonly used in seawater? A) CSE B) Ag/AgCI C) Calomel D) Zinc E) SHE b