MCDs On Corrosion Chemistry PDF

MCDs On Corrosion Chemistry 1-Corrosion take place when two metallic phases with different electrochemical potential True False 2- potential differences may also arise because of impurities, internal stresses, corrosion products, damaged productive coatings True False 3- ln the initial stage of rust...

MCDs On Corrosion Chemistry 1-Corrosion take place when two metallic phases with different electrochemical potential True False 2- potential differences may also arise because of impurities, internal stresses, corrosion products, damaged productive coatings True False 3- ln the initial stage of rusting, some iron atoms lose electrons to become Fe2+ True False 4- The chemical reaction of forming the hydroxide or oxide layer is the cause of producing the " rust." True False 5- Acid solution make rusting go faster True 1 False 6) Which of the following metal does not corrode? a) copper b) Zinc c) iron d) Magnesium 7)What is the chemical formula of rust? (a) Fe2O3. xH2O (b) Fe3O4. xH2O (c) Both (a) and (b) (d) None of the above 8)Which of the following factor influences the rate and extent of corrosion? a) Nature of metal of metal and environment b) Nature of the environment only c) nature of metal only d) Nature of reaction 9) The rusting of iron speeds up in the presence of salt( ) answer: True 10)An increase of temperature increase rate of corrosion ( ) answer: True 2 11)Sodium chloride make iron rust more quickly ( ) answer: True 12)When iron is in contact with a less reactive metals , it corroded ( ) Answer: True 13) Rusting can be prevented by.......... a) All of them b)alloying C) galvanizing d) coating 14) Galvanizing is the process of coating iron with..... (a) zin (b) Tin (c) Copper (d) Nickel 15) The steel structures are protected electrically by connecting them to Negative terminal True False 16) Steel can be alloyed with....... 17) to produce stainless steels a) chromium and nickel b) carbon and nickel c) Zinc and chromium d) None of them 3 18) Tin - plate is iron coated with..... a) Tin b) Zinc c) nickel c) Copper 19) Rusting is a redox reaction True False 20) In cathodic protection iron act as anode False True 21-What is the primary cause of local action in a battery cell? (a) Impurities in the metal (b) Impurities in the electrolyte (c) Overcharging of the battery (d) High temperature 22-In local action cell, current is carried out in metallic bath by.......... While through the electrolyte by....... (a)electrons, positive or negative ions (b) electrons, positive ions (c) negative ions, electrons (d) ions, electrons 23-The corrosion of the ultra-pure metals occurs when the potential difference at the metal/interface is...... than the equilibrium potential of...... (a) more positive, metal reduction 4 (b) less positive, metal reduction (c) more negative, metal oxidation (d) less negative, metal oxidation 24-Local action cell theory is also called....... theory of corrosion (a) Heterogeneous (b) Homogeneous (c) Acid (d) None of them 25-When the anodic and cathodic reaction occur over the metal surface randomly in space and time, this is called.... (a) Homogeneous theory of corrosion (b) Heterogeneous theory of corrosion (c) all of them (d) none of them 26. In an aqueous solution, the electron acceptors are: a. Oxygen and dissolved oxygen b. Nitrogen and Hydrogen c. Water and Oxygen d. Oxygen and Carbon 27. The stability of metals can be determined based on: a. The equilibrium thermodynamics b. The temperature of the metal c. The color of the metal 5 d. The hardness of the metal 28. According to thermodynamic equations, more negative potential metals: a. Are more reactive. b. Are less reactive. c. Are unstable. d. Are not affected by corrosion. 29. What does the potential-pH diagram help predict for metals? a. Corrosion tendency b. Reactivity to heat c. Electrolyte concentration d. Oxidation rate 30. An electrode with negative E° acts as the: a. Anode b. Cathode c. Generator d. Electrolyte 31. The potential variation of an oxygen electrode with pH is represented by a line with a slope of: a. 0.06 b. 0.12 c. 0.24 d. 0.32 6 32. What does a potential-pH diagram represent? a. Stability of metals b. Reactivity with metals c. Electron movement d. Corrosion rate 33. What is the slope of the potential variation line of an oxygen electrode with pH? a. -0.06 b. -0.12 c. 0.06 d. 0.12 34. A reaction involving both electrons and protons will vary its equilibrium potential with: a.pH b. Electrolyte charges c. Catalysts d. Metal type 35.which method occurs by brief immersion in a molten bath of metal ? a) Hot dipping. b) Electro plating. c) Gas-phase reaction. d) Metal spraying. 36. The way that provides protection by forming an electrically conductive coating and are pigmented with metallic Zinc? a) Zinc-Rich Coating. 7 b) Phenolic coating. c) Epoxy coating. d) Oil coating. 37. Which of the following metals is commonly used as a sacrificial anode in cathodic protection? a) Zinc b) Aluminum c) Copper d) Gold 38. How does impressed current cathodic protection work? a) By applying a voltage to the structure to create a protective current b) By burying sacrificial anodes near the structure c) By coating the structure with a protective layer d) By removing oxygen from the environment 39. Which type of cathodic protection is often used for underground pipelines? a) Sacrificial anode b) Impressed current c) Galvanic corrosion d) Passivation 40. What is the primary mechanism by which cathodic protection prevents corrosion? a) Reduction of the corrosion potential b) Alteration of the pH level c) Creation of a physical barrier 8 d) Increase in the temperature of the environment 41. The primary function of a corrosion inhibitor in an aqueous environment is to: a) Form a protective film on the metal surface, hindering the corrosion reaction. b) Increase the rate of the corrosion process. c) Reduce the electrical conductivity of the electrolyte. d) Remove existing corrosion products from the metal surface. 42. Corrosion inhibitors can be classified based on their mechanism of action. Which of the following mechanisms is MOST associated with Type A inhibitors? a) Adsorption on the metal surface, creating a barrier to corrosive species. b) Anodic passivation, forming a protective oxide layer on the metal. c) Cathodic poisoning, reducing the activity of cathodic sites on the metal surface. d) Film formation by precipitation of a sparingly soluble inhibitor salt on the metal. 43. The effectiveness of a corrosion inhibitor can be influenced by several factors. Which of the following is generally NOT a desirable characteristic for an ideal corrosion inhibitor? a) High volatility (easily evaporates) b) Low cost and easy availability c) High solubility in water d) Chemically reactive with the metal surface (can lead to unintended side effects) 44. In some cases, the use of corrosion inhibitors can have drawbacks. Which of the following is a potential disadvantage of using corrosion inhibitors? a) They can be environmentally harmful if not properly disposed of. b) They may interfere with other surface treatment processes. c) They can be ineffective in highly corrosive environments. 9 d) All of the above 45. When selecting a corrosion inhibitor for a specific application, it's crucial to consider various factors. Which of the following is the MOST important factor to consider? a) The compatibility of the inhibitor with the metal, corrosive environment, and desired application conditions b) The brand name of the inhibitor c) The ease of application of the inhibitor d) The cost of the inhibitor 46)Which of the following thermodynamic parameters indicates a spontaneous corrosion reaction? A) ΔG° < 0 B) ΔG° > 0 c) ΔH° > 0 d) ΔS° < 0 47)A negative value of ΔG° for a corrosion reaction implies: a)Thermodynamic favorability for corrosion b) Immunity of the metal c) Faster corrosion rate d) Slower corrosion rate 48)The equilibrium constant (K) in the Nernst equation is related to the: a) Standard electrode potential b)Electrode potential of the metal c) Concentration of reactants d) Rate of corrosion 10 49)In a galvanic corrosion cell, the metal with the: a) More positive electrode potential is the anode b) More negative electrode potential is the anode c) Higher corrosion rate is the cathode d) Lower corrosion rate is the cathode 50)The Pourbaix diagram is a useful tool for predicting the: a) Thermodynamics of corrosion reactions b) Kinetics of corrosion reactions c) Morphology of corrosion products d) Effectiveness of corrosion inhibitors 51)In a Pourbaix diagram, the immunity region corresponds to: a) Thermodynamic stability of the metal b) Oxidation of the metal c) Reduction of the metal ions d) Rapid corrosion 52)The rate of corrosion can be determined using thermodynamic data: a) Directly b) Only qualitatively c) Not at all 53)Which of the following regions in a Pourbaix diagram indicates the most favorable conditions for the corrosion of a metal? a) Oxidation zone 11 b) Passivity zone c) Reduction zone d) Immunity zone 54)In a Pourbaix diagram, the vertical axis represents: a)Electrode potential (Eh) b) Temperature c) Concentration of the metal ions d) Current density 55)Which of the following statements about current-potential curves in electrochemical studies is correct? A) Current-potential curves display the relationship between the applied potential and resulting current, offering insights into the electrochemical behavior and corrosion susceptibility of a material. B) *Current potential* curves provide information about the mass of metal lost due to corrosion but do not indicate the corrosion rate. C) Current-potential curves illustrate the relationship between temperature and corrosion potential for a given metal. D) Current-potential curves are primarily used to determine the mechanical properties of a metal and are not relevant to its corrosion behavior. 56)Which of the following statements regarding corrosion current and corrosion potential is true? A) Corrosion current is the rate at which corrosion occurs, while corrosion potential is the tendency for a metal to corrode. B) Corrosion potential is the rate at which corrosion occurs, while corrosion current is the tendency for a metal to corrode. C) Corrosion potential and corrosion current are two terms for the same phenomenon. 12 D) Corrosion potential and corrosion current are unrelated to each other in the context of corrosion. 57)Which of the following statements about Evans diagrams in the context of corrosion is correct? A) Evans diagrams depict the corrosion potential and corrosion current density for a metal in a specific environment. B) Evans diagrams illustrate the rate of corrosion for different metals but do not provide information about corrosion mechanisms. C) Evans diagrams are used exclusively in laboratory settings and have no practical application in real-world corrosion prevention. D) Evans diagrams are only applicable to certain types of corrosion, such as galvanic corrosion, and are not relevant to other forms of corrosion. 58)Which type of Evans diagram represents a situation where the cathodic reaction rate is controlled by the rate of mass transport of the reacting species to the electrode surface? A) Type II B) Type I C) Type III D) Type IV 59) How many methods of determining the corrosion rate? A) 4 B) 2 C) 3 D) 1 60) What is the basic principle of the weight loss method for determining corrosion rate? A) Measuring the change in the weight of a metallic sample 13 B) Measuring the volume of H₂ evolved C) Measuring the change in the area of a metallic sample D) Measuring the temperature change in the corrosive media 61) What does the variable 'A' represent in the corrosion rate formula K.W/A.T.D? A) Area in cm² B) Weight loss C) Time D) Density in g/cm² 62) Which of the following units is used to express corrosion rate? A) mils per year (mpy) B) g/cm² C) kg/m² D) meters per second 63) How is the corrosion rate evaluated for metallic materials in non-oxidizing media? A) By measuring the volume of H₂ evolved B) By measuring the weight loss of the sample C) By measuring the temperature change in the corrosive media D) By measuring the change in color of the sample 64) What is the purpose of comparing results with and without the addition of an inhibitor in the corrosion rate experiment? A) To determine the efficiency of the inhibitor B) To measure the temperature change C) To measure the change in density 14 D) To determine the area of the sample 65) What is the primary purpose of the Thermometric Method (Mylius method)? A. To compare the corrosion rate and inhibition efficiency of various inhibitors. B. To determine the boiling point of a corrosive media. C. To measure the density of a metal. D. To test the electrical conductivity of Al and Al alloys. 66) What is the initial step in the Mylius method? A. Dropping a test piece of the metal into a definite volume of corrosive media. B. Heating the metal test piece. C. Measuring the electrical resistance of the metal. D. Cooling the metal test piece. 67) What does the reaction number (R.N.) represent in the Mylius method? A. The corrosion rate of the metal B. The amount of heat generated during the reaction. C. The weight loss of the metal D. The pH changes of the corrosive media 68) How is the reaction number (R.N.) calculated in the Mylius method? A. R.N. = (Tm - Ti) / t B. R.N. = (Tm + Ti) / t C. R.N. = (Ti - Tm) / t D. R.N. = Tm * Ti / t 15 69) What happens to the reaction number (R.N.) when an organic inhibitor is added to the corrosive media? A. It decreases. B. It increases. C. It remains the same. D. It fluctuates. 70) In the formula R.N. = (Tm - Ti) /t, what does Tm stand for? A. Maximum temperature B. Minimum temperature C. Initial temperature D. Time in minutes 71) In the formula R.N. = (Tm - Ti) / t, what does Ti stand for? A. Initial temperature B. Maximum temperature C. Time in minutes D. Corrosive media volume 72) What is the sensitivity of the radiochemical method for detecting corroding metal? a) 10^-10 gm b) 10^-6 gm c) 10^-3 gm 16 d) 10^-15 gm 73) What is the purpose of using labelled metal in the radiochemical method? a) To determine the corrosion rate b) To change the color of the metal c) To increase the metal's strength d) To make the metal resistant to corrosion 74) Which instrument is used to detect the radiation emitted in the radiochemical method? a) Geiger-Müller (GM) counter b) atomic absorption spectrometer c) Spectrophotometer d) Scanning electron microscope 75) What is the significance of the Tafel slope in the Tafel equation? A) It quantifies the overpotential required for the reaction. B) It indicates the rate at which the reaction proceeds. C) It represents the exchange current density. D) It determines the activation energy of the reaction. 76) What does the Tafel equation describe? A) The relationship between potential and current in electrochemical cells. B) The relationship between current and time in electrochemical cells. C) The relationship between potential and time in electrochemical cells. D) The relationship between temperature and reaction rate in electrochemical cells. 17 (77) Water Is Essential Medium for Corrosion a) false b)true (78) Thermodynamically Cannot Be Expected the Corrosion a)false b)true (79) The Decay Of Metal Mass With Time Is Called Rusting a)false b)true (80)Immunity Means That The Area Which Metal Under Study Is Act As Anode a)false b)true (81)With Acidic Medium the Metals Still Protected From Corrosion a)false b)true (82)On the Surface of Most Metal There Are Different Points Of Different Potential , This Is The Local Cells a)true b)false (83)Corrosion Rate Increase with The Increasing Of Acidity Of Medium a)true 18 b)false (84)At PH More Than 10 , Zn Metal Is Protected Due To Formation Of Zincate Layer a)false b)true (85)V - PH Diagram Give Information On The Regions Of Corrosion a)True b)false (86)The Corrosion Process Means Reduction Of Metals a)false b)true (87)Which of the following factors is NOT necessary for filiform corrosion to occur? (a) Oxygen (b) Salts (c) Acids (d)Moisture (88)Which of the following metals is most susceptible to filiform corrosion? (a) Aluminum (b) Steel (c) Copper (d) Nickel (89)Which of the following is the best way to prevent filiform corrosion? 19 (a) All of the above. (b) Maintain the paint or coating regularly. (c) Use a cathodic protection system. (d)Use a high-quality paint or coating. (90)How is filiform corrosion diagnosed? (a) All of the above (b) Ultrasonic testing (c) X-rays (d)Visual inspection (91)How is filiform corrosion treated? (a) The treatment depends on the severity of the corrosion. (b) Remove and replace the paint or coating. (c) Use a cathodic protection system. (d)Repair any cracks or peeling in the paint or coating. (92) Filiform corrosion is a type of localized corrosion that occurs under a thin layer of paint or coating on a metal surface. a-True b-Fase (93) Filiform corrosion is only caused by water. a-False b-true (94) Filiform corrosion can be prevented by using a high-quality paint or coating. 20 a-True b-false (95) Filiform corrosion is easy to detect because it causes visible swelling or blistering of the paint or coating. a-False b-true (96) The cost of treating filiform corrosion can vary depending on the severity of the corrosion and the size of the affected area. a-True b-false 97. The rusting of iron is catalyzed by which of the following.... C) O2 B) Zn A) H+ D) Fe 98. The rate of corrosion of iron in atmosphere depends on..... D) Frequency of rainfall B) Humidity of air C) Intensity of atmosphere pollution A) All 99. Electrochemical corrosion can occur only when... B) Air is in contact with metal A) Liquid medium is in contact with metal 21 C) Oxygen is in contact with metal D) None 100. Chemical corrosion always takes place in B) Anodic and Cathodic area A) Anodic area C) Cathodic area metal D) Interior of metal 101. A galvanic cell converts.. A) Chemical energy into Electrical energy B) Electrical energy into Chemical energy C) Electrical energy into Heat energy D) Chemical energy into Heat energy 102. Corrosion is an example of..... A) Oxidation B) Redaction C) Electrolysis D) Electrolysis 103. Which of the following metal oxide film is protective from corrosion.... B)Porous A) Non-porous C) Volatile D) unstable 22 104. Which type of the metal oxide film causes rapid and continuous corrosion.... C) Non-porous and Adherent B) Stable and Non-porous A) Porous or Volatile D)None of these 105. Electrochemical corrosion in acidic environment is carried with.... B) O2 evolution B) O2 absorption A) H2 evolution D) H2 absorption 106. During galvanic corrosion, the most noble metal acts as... B) Anode as well as Cathode A) Cathode C) Anode D) Both B & C 107. Iron corrodes faster than aluminum due to B) Al reacts with medium A) Al forms protective oxide film C) Al is lighter than Fe D) None 108. Impure metal corrodes faster than pure metal due to B) Homogeneity 23 A) Heterogeneity C) Both D) None 109-The process of dipping a metal object into a molten metal bath to create a coating is called: a) Hot dipping (Galvanizing) b)Electro plating c) Cladding d) Cementation 110-Which of the following is an advantage of using metallic coatings? a) Improved corrosion resistance b)Electrical insulation c) Lower thermal conductivity d) Increased surface roughness 111-Electroplating deposits a metallic coating using: a) An electric current b)High temperature c) Chemical reactions d) A mechanical spray 112-A disadvantage of metallic coatings compared to some non-metallic coatings can be: a) Higher weight of the coated object b)Lower cost c) Brittleness of the coating 24 d) Difficulty in achieving a uniform thickness 113-An application where metal spraying (thermal spraying) would be a good choice is: a)Repairing worn-out machine parts b) Coating wires for electrical applications c) Protecting underground pipes d) Creating a reflective surface on a mirror 114. According to the local action cell theory, what are the two key areas involved in corrosion? (A) Anode and cathode (B) Electrons and protons (C) Nucleus and cloud (D)None of them 115. What is the role of the cathode in the local action cell theory? (A) It is the electron source where an oxygen reduction reaction often occurs. (B) It is the electron sink where metal dissolves. (C) It is the area where the metal is protected. (D) It does not exist in this theory. 116. How does the local action cell theory explain the effect of impurities on corrosion? (A) Impurities can create concentration cells, accelerating corrosion. (B) Impurities can act as protective barriers, slowing down corrosion. 25 (C) The theory does not account for the effect of impurities. (D) Impurities have no effect on the overall corrosion process. 117. According to the homogeneous theory of corrosion, where do metal dissolution and electronation reactions occur? (A) Randomly across the entire metal surface (B) Only at specific anodic and cathodic sites (C) In a thin layer of oxide film on the metal surface (D) Evenly throughout the bulk of the metal 118.What is the driving force for corrosion according to the homogeneous theory? (A) The inherent instability of the metal surface (B) The presence of an external electric current (C) The formation of a concentration gradient (D) The depletion of oxygen at the metal surface 119.How does the homogeneous theory differ from the local action cell theory in terms of the required conditions for corrosion? (A) The homogeneous theory does not require distinct anodic and cathodic sites. (B) The homogeneous theory requires a larger surface area for corrosion to occur. (C) The homogeneous theory only applies to specific types of metals. (D) The homogeneous theory is not affected by the presence of electrolytes. 120. Metals with a more positive electrode potential are generally considered: (A) More passive and more resistant to corrosion (B) More active and more prone to corrosion 26 (C) More likely to act as anodes (D) Not affected by the concept of electrode potential 121.A metal pipe with a scratch is buried in soil. The scratch exposes a small area of bare metal. According to the local action cell theory, which area of the pipe is more likely to corrode? (A) The area of the exposed metal (This area acts as the anode and is more prone to corrosion) (B) The area of the pipe covered by soil (C) Both areas will corrode at the same rate. (D) The effect of the scratch cannot be determined from the information provided. 122. A storage tank made of steel is coated with a layer of zinc. Which theory best explains the protective effect of the zinc coating? (A) Local action cell theory: The zinc acts as a sacrificial anode, corroding preferentially to protect the steel. (B) Homogeneous theory: The zinc coating creates a barrier that prevents the metal from reacting with the environment. (C)A,B (D)None of them 123.Which of the following is an example of an inorganic coating? a)Enamel b) Paint c) Varnish d) Lacquer 124.Electroplating is a type of protective coating that involves: 27 a) Depositing a metal layer through an electric current b) Applying a pre-formed coating film through heat and pressure c) Chemically converting the substrate surface d) Spraying a liquid coating material that dries to form a film 28