165 + Interview Questions in Eight Forms Of Corrosion in Corrosion Engineering Page 2 InterviewSolution

51.	What is the nature of fatigue fracture?(a) Brittle fracture(b) Cup and cone fracture(c) Tensile fracture(d) Brittle and tensile fractureThe question was posed to me during an interview.My doubt is from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» CORRECT ANSWER is (a) Brittle fracture Best explanation: A fatigue CRACK propagates until the cross-sectional AREA of the metal is reduced to the point where the ultimate strength is exceeded and rapid brittle fracture OCCURS. The nature of fatigue fracture is brittle.

Discussion

52.	Corrosion fatigue is defined as the reduction of fatigue resistance due to the presence of a corrosive medium.(a) True(b) FalseI got this question during an interview.Origin of the question is Eight Forms topic in section Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT choice is (a) True For explanation I WOULD say: Corrosion fatigue is a SIMULTANEOUS action of corrosion and fatigue on a METAL. It is defined as the reduction in fatigue resistance DUE to the presence of a corrosive medium.

Discussion

53.	Which of the following types of hydrogen damage processes are high-temperature processes?(a) Hydrogen blistering and hydrogen attack(b) Hydrogen attack and Decarburization(c) Decarburization and hydrogen embrittlement(d) Hydrogen attack onlyI had been asked this question by my college director while I was bunking the class.Question is from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» Right option is (B) Hydrogen attack and Decarburization The best EXPLANATION: Hydrogen attack and decarburization are HIGH-temperature processes. Decarburization refers to the removal of carbon from METAL, is often produced by moist hydrogen at high temperatures. Hydrogen attack refers to the interaction of hydrogen and metal at high temperatures.

Discussion

54.	Which of the following is/are the environments that cause stress-corrosion cracking to titanium?(a) Red fuming nitric acid(b) Methanol-HCl(c) Nitrogen tetroxide (N2O4)(d) Red fuming nitric acid, methanol-HCl, and nitrogen tetroxideI had been asked this question in unit test.This intriguing question comes from Eight Forms topic in division Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct choice is (d) Red fuming NITRIC acid, methanol-HCl, and nitrogen tetroxide To EXPLAIN I would say: Stress-CORROSION cracking is the simultaneous action of stress and corrosive environment on a metal. Red fuming nitric acid, methanol-HCl, and nitrogen tetroxide are the environments that may cause stress-cracking corrosion.

Discussion

55.	Which of the following characteristics of titanium, makes it resistant to erosion-corrosion?(a) Stability of titanium oxide(b) Instability of titanium oxide(c) The low reactivity of titanium(d) The low reactivity of titanium and instability of titanium oxideThe question was asked in an interview for internship.My query is from Eight Forms in division Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct ANSWER is (a) Stability of TITANIUM oxide The EXPLANATION: Titanium is a reactive METAL but is resistant to erosion-corrosion in many environments because of the stability of the titanium oxide (TiO2) film. It reforms its oxide LAYER within a fraction of seconds after wearing out.

Discussion

56.	Which of the following type of stress has an important role in rupturing protective films during both the initiation and propagation of cracks?(a) Tensile stress(b) Compressive stress(c) Shear stress(d) Compressive and shear stressI got this question during an interview.Enquiry is from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» CORRECT option is (a) Tensile stress To explain I would say: Tensile stress has an IMPORTANT role in rupturing protective films during both the initiation and propagation of CRACKS. Breaks in the passive layer of metal INDUCE a RAPID attack.

Discussion

57.	Which of the following is/are the basic requirements for the occurrence of fretting corrosion?(a) The interface must be under load(b) Vibration or repeated relative motion between the two surfaces(c) The interface must be under load and vibration or repeated relative motion between the two surfaces(d) The relative motion should be highI got this question during an online interview.This question is from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct option is (c) The interface must be under load and VIBRATION or repeated relative MOTION between the two surfaces For explanation: The basic requirements for the occurrence of FRETTING corrosion are: i. The interface must be under load ii. Vibration or repeated relative motion between the two surfaces iii. The load and the relative motion of the interface must be sufficient to PRODUCE deformation.

Discussion

58.	Which of the following alloys exhibits intergranular corrosion by steam and marine atmospheres?(a) Die-cast zinc alloy(b) Duralumin alloy (Al-Cu)(c) Both die-cast zinc alloy and duralumin alloy(d) Neither die-cast zinc alloy nor duralumin alloyThis question was posed to me in a national level competition.Asked question is from Eight Forms in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT choice is (a) Die-cast ZINC alloy For explanation: Die-cast zinc alloys containing aluminum exhibit intergranular CORROSION by steam and marine atmosphere. Whereas duralumin alloys are ALSO susceptible to intergranular corrosion in a different atmosphere.

Discussion

59.	Which of the following is/are the methods to control intergranular corrosion of austenitic stainless steel?(a) Employing solution-quenching(b) Adding stabilizers(c) Lowering the carbon content to below 0.03%(d) Employing solution-quenching, adding stabilizers and lowering the carbon content to below 0.03%I had been asked this question in quiz.This question is from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct option is (d) EMPLOYING solution-quenching, adding stabilizers and lowering the carbon content to below 0.03% The EXPLANATION is: AUSTENITIC STAINLESS steels are highly PRONE to intergranular corrosion. It can be minimized by i. Employing quench-annealing or solution-quenching ii. Adding stabilizers that forms strong carbides iii. Lowering the carbon content to below 0.03%

Discussion

60.	Which of the following term is associated with intergranular corrosion in welded structures?(a) Intergranular weld(b) Weld failure(c) Weld decay(d) Weld corrosionI got this question by my school teacher while I was bunking the class.Question is from Eight Forms topic in section Eight Forms of Corrosion of Corrosion Engineering
Answer» Right choice is (c) Weld decay Explanation: The intergranular corrosion ASSOCIATED with the welded STRUCTURES and METALS is KNOWN as weld decay. The depletion of alloying takes place adjacent to the weld bead as it EXPOSED to high temperature (sensitization temperature).

Discussion

61.	What is the abbreviation of EMF?(a) Electromagnetic force(b) Electromotive frequency(c) Electromotive force(d) Electrode motive forceThis question was posed to me in an internship interview.My query is from Eight Forms in division Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (c) ELECTROMOTIVE force The best EXPLANATION: EMF is abbreviated as an electromotive force. It is defined as the POTENTIAL difference between two points (cathode and anode) in a CIRCUIT. It is the cause of the flow of current in the circuit.

Discussion

62.	Which of the following type of corrosion is localized in nature?(a) Crevice corrosion(b) Galvanic corrosion(c) Uniform corrosion(d) Inter-granular corrosionI have been asked this question in unit test.I would like to ask this question from Eight Forms in section Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (a) Crevice corrosion The best I can explain: Crevice corrosion is localized corrosion because it OCCURS only at discrete sites on the metal surface.This occurs due to the presence of a stagnant SOLUTION in crevices (small spaces). This crevice CORRODES RAPIDLY by cathodically protecting adjacent surfaces.

Discussion

63.	What is the standard electrode potential of Fe^+2/Fe?(a) 0.0 V(b) +0.36(c) -0.44(d) -0.76The question was posed to me in examination.My question is based upon Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct answer is (c) -0.44 To explain: Standard reduction POTENTIAL of hydrogen ION, COPPER, IRON, and zinc Is 0.0V, +0.36V, -0.44V and -0.76V respectively. These are measured against the standard hydrogen electrode (SHE) which arbitrarily defined as ZERO.

Discussion

64.	Which of the following characteristics of the impoverished area, results in a rapid corrosion attack?(a) Less corrosion resistance(b) The high content of chromium(c) The large unfavorable area ratio(d) Less corrosion resistance and large unfavorable area ratioThis question was posed to me during an online exam.This intriguing question originated from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT answer is (d) Less corrosion RESISTANCE and large unfavorable area ratio The best explanation: Rapid corrosion attack in impoverished or chromium depleted zone is due to i. Less corrosion resistance (As chromium% is decreased) ii. Two DISSIMILAR metal COMPOSITIONS are in contact (GALVANIC effect) iii. Large unfavorable area ratio is present (Area effect)

Discussion

65.	What is the minimum percent of chromium is needed to make stainless steel?(a) 2%(b) 20%(c) 1%(d) 11%This question was posed to me during an interview.This is a very interesting question from Eight Forms in section Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct option is (d) 11% For explanation I WOULD SAY: Stainless STEEL is a family of iron-based alloys that contain a minimum of 11% chromium. Chromium IMPARTS corrosive RESISTANCE to steel. There are 4 types of stainless steel. They are i. Austenitic stainless steels ii. Martensitic stainless steels iii. Ferritic stainless steels iv. Duplex stainless steels

Discussion

66.	Which of the following are the reasons that make it difficult to detect pits?(a) Small size(b) Varying depths(c) Pits covered with corrosion products(d) Small size, varying depths and covered with corrosion productsThe question was posed to me in my homework.This is a very interesting question from Eight Forms topic in section Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct option is (d) Small size, varying depths and COVERED with corrosion products To explain: It is DIFFICULT to measure the pitting quantitatively because of its small size, varying DEPTH, and due to covered corrosion products. It fails the equipment because of perforation over the entire SURFACE with only a small PERCENT weight loss.

Discussion

67.	What are the preventions of filiform corrosion?(a) Use of coatings with low water permeability(b) To store in low-humidity environment(c) To store in high-humidity environment(d) Use of coatings with low water permeability and to store in a low-humidity environmentThe question was posed to me in final exam.I want to ask this question from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct choice is (d) Use of coatings with low WATER permeability and to store in a low-humidity environment The best explanation: Filiform corrosion is a SPECIAL type of crevice corrosion, OCCURS under METAL coatings in a relatively high-humidity environment Preventions to filiform corrosion: i. Use of coatings with low water permeability ii. To store in a low-humidity environment iii. Use of brittle films or coatings

Discussion

68.	Which of the following corrosion testing describe the test for crevice corrosion?(a) Occluded cell corrosion(b) Galvanic effect(c) Atmospheric exposure testing(d) Kesternich chamber testingI got this question during an interview.My question is based upon Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct OPTION is (a) Occluded cell corrosion The explanation is: Occluded cell corrosion is a corrosion testing that DESCRIBES crevice corrosion. In this test, a NARROW gap is maintained between two metal in a STAGNANT corrosive solution. An occluded cell is also KNOWN as crevice corrosion.

Discussion

69.	Which of the following metal is highly resistant to crevice corrosion?(a) Stainless steel(b) Copper(c) Aluminum(d) Hastelloy C-276I have been asked this question by my college director while I was bunking the class.The above asked question is from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (d) Hastelloy C-276 Explanation: Hastelloy C-276 is the best CREVICE CORROSION-resistant metal. The COMPOSITION of Hastelloy C-276 is 15.5%Cr, 54.7%Ni, 15.5%MO, 3.8%W, and 0.5%Mn. Whereas the other metals depend on oxide film for their corrosion resistance.

Discussion

70.	Which of the following is the other name of crevice corrosion?(a) Filiform corrosion(b) Deposit or gasket corrosion(c) Two-metal corrosion(d) Surface corrosionThis question was addressed to me during a job interview.My doubt stems from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Right CHOICE is (b) Deposit or GASKET corrosion Easiest explanation: CREVICE corrosion occurs due to the presence of a STAGNANT SOLUTION in the crevices. These crevices are formed due to the corrosion deposits or gaps at the metal-gasket interface. Thus, it is also called as deposit or gasket corrosion.

Discussion

71.	Which of the following is an example of cathodic protection?(a) Electroplating of steel(b) Galvanization of steel(c) Magnesium connected to steel pipes(d) Electroplating of steel, galvanization of steel and magnesium connected to steelI have been asked this question during an online exam.This interesting question is from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (d) Electroplating of steel, galvanization of steel and magnesium connected to steel The best I can explain: Electroplating and galvanization are cathodic protections of steel based on the galvanic EFFECT. If steel under zinc or other METAL coating exposed to corrosive ATMOSPHERE, zinc corrodes preferentially than steel. Magnesium ACTS as a sacrificial anode when it is connected to underground steel pipes.

Discussion

72.	Which of the following electrolyte is used for the preparation of a general galvanic series?(a) Polluted seawater(b) Unpolluted river water(c) Polluted river water(d) Unpovlluted seawaterThis question was posed to me in a national level competition.The doubt is from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Right CHOICE is (d) Unpovlluted seawater Easy explanation: Galvanic series is the most ACCURATE PREDICTION of galvanic relationships of metals. It is BASED on potential measurements and galvanic corrosion tests in unpolluted seawater. This INCLUDES metals and alloys along with their active and passive states.

Discussion

73.	The reason for the noble nature of titanium is that it cathodically polarizes readily in seawater.(a) False(b) TrueThis question was posed to me in exam.This interesting question is from Eight Forms in division Eight Forms of Corrosion of Corrosion Engineering
Answer» Right OPTION is (B) True To explain I would SAY: Titanium is one of the noble METALS in the galvanic series and the reason is that it cathodically polarizes readily in seawater. It replaces many materials as best corrosive resistant METAL in the seawater applications and high-velocity corrosive solutions.

Discussion

74.	What are the conditions to measure the standard reduction potential of metals against SHE?(a) 2 atm pressure, 25°C temperature, 2M concentration of H^+(b) 2 atm pressure, 25°C temperature, 1M concentration of H^+(c) 1 atm pressure, 25°C temperature, 1M concentration of H^+(d) 1 atm pressure, 25°C temperature, 2M concentration of H^+I have been asked this question in an online quiz.I want to ask this question from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Right choice is (c) 1 atm pressure, 25°C temperature, 1M concentration of H^+ Explanation: The conditions to measure the standard reduction potential of METAL electrodes against standard hydrogen electrode (SHE) are 1 atmospheric pressure, 25°C temperature and 1 molarity concentration of H^+ IONS.

Discussion

75.	Which of the following is the primary characteristic of an electrolyte to form corrosion?(a) Electrical resistivity(b) Thermal resistivity(c) Thermal conductivity(d) Electrical conductivityI had been asked this question by my school teacher while I was bunking the class.My question comes from Eight Forms in division Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT option is (d) ELECTRICAL conductivity For explanation I would SAY: Electrical conductivity is the primary characteristic of an electrolyte. Electrolyte is a medium to transfer ELECTRONS from anode to CATHODE, this results in corrosion. The conductivity of the electrolyte is one of the main factors in the regulation of corrosion.

Discussion

76.	Which of the following acid that results in selective removal of aluminum in aluminum bronzes?(a) Hydrochloric acid (HCl)(b) Hydrofluoric acid (HF)(c) Nitric acid (HNO3)(d) Hydrochloric, hydrofluoric and nitric acidI got this question during an interview.The query is from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (b) Hydrofluoric acid (HF) To elaborate: Selective Leaching is the removal of one element from a solid ALLOY by the corrosion process. And selective removal of ALUMINUM from aluminum bronzes can be RESULTED by USING hydrofluoric acid.

Discussion

77.	Which of the following phenomenon that results in the dissolution of iron by leaving porous graphite on the surface of grey cast iron?(a) Dezincification(b) Decalcification(c) Graphitization(d) Dezincification and graphitizationThis question was posed to me in homework.My enquiry is from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Right answer is (c) Graphitization The explanation: GRAPHITE is cathodic to iron in grey CAST iron that results in the dissolution of iron by LEAVING porous graphite in a MILD corrosive solution. This phenomenon is KNOWN as graphitization.

Discussion

78.	Which of the following is/are the types of dezincification?(a) Layer-type(b) Plug-type(c) Layer-type and Plug-type(d) Neither Layer-type nor Plug-typeI got this question in an international level competition.This key question is from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The CORRECT option is (C) Layer-type and Plug-type The BEST I can explain: There are two common types of DEZINCIFICATION types. They are i. Layer-type or UNIFORM ii. Plug-type or localized

Discussion

79.	Numerous failures of 18-8 Stainless steel have occurred in the temperature range of 950 to 1450°F(a) True(b) FalseThis question was posed to me during an internship interview.My doubt is from Eight Forms in section Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT option is (a) True To elaborate: Numerous failures of 18-8 stainless steel have occurred in the temperature RANGE of 950 to 1450°F. When these steels are heated in the range of 950 to 1450°F they become sensitized or susceptible to intergranular CORROSION due to the depletion of chromium at the grain boundary.

Discussion

80.	Pitting is a form of extremely localized attack that results in holes in the metal.(a) True(b) FalseThe question was asked in an internship interview.This intriguing question comes from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct choice is (a) True The explanation: Pitting and CREVICE corrosion are the localized corrosion types, that RESULTS in the corrosion on very confined CORROSIVE sites. Localized attack of pitting results in holes in the metal.

Discussion

81.	The difference in metal ion or oxygen concentration between the crevice and its surroundings is the main reason for crevice corrosion.(a) True(b) FalseThis question was addressed to me in an interview for job.The query is from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Right OPTION is (a) True Best explanation: Crevice corrosion is MAINLY OCCURRED due to the difference in metal ion or OXYGEN concentration between the crevice and its SURROUNDINGS. This is due to the unavailability of oxygen in the crevice, this results in the dissolution of metal in a crevice by protecting adjacent surface cathodically.

Discussion

82.	What is the standard reduction potential value of gold in the EMF series?(a) +1.498 V(b) +1.2 V(c) +0.987 V(d) +0.799 VThe question was asked by my college professor while I was bunking the class.Query is from Eight Forms in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The CORRECT answer is (a) +1.498 V For explanation: STANDARD reduction potential values of METAL are measured against SHE. Standard reduction potential of gold (Au-Au^+3), PLATINUM (Pt-Pt^+2), palladium (Pd-Pd^+2), SILVER (Ag-Ag^+1) are +1.498V, +1.2V, +0.987V and +0.799V respectively.

Discussion

83.	Which of the following metal is more susceptible to crevice corrosion?(a) Titanium(b) Hastelloy C(c) Stainless steel-430(d) Titanium and stainless steelI have been asked this question in a national level competition.My question is from Eight Forms topic in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (c) Stainless steel-430 To explain I would SAY: Stainless steel-430 is highly prone to CREVICE corrosion. The reasons are as follows: 1. Large critical current density 2. Wide active-passive transitions 3. LIMITED passive REGION

Discussion

84.	Corrosion is greater near the seashore than in a dry rural atmosphere.(a) True(b) FalseThe question was asked in class test.This is a very interesting question from Eight Forms in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct answer is (a) True To explain I would say: Corrosion occurs DUE to the PRESENCE of oxygen and moisture (electrolyte). The electrical CONDUCTIVITY of the electrolyte is one of the factors of corrosion. Corrosion increases with an increase in electrical conductivity of the electrolyte. Moisture with salt content RELATIVELY has high electrical conductivity, hence corrosion is greater at the SEASHORE.

Discussion

85.	The potential generated by two dissimilar metal combinations can change with time.(a) True(b) FalseI have been asked this question in quiz.My doubt stems from Eight Forms in section Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct answer is (a) True Easy EXPLANATION: The potential developed between two DISSIMILAR metals is usually DECREASES. This is due to the accumulation of reaction or corrosion products at the anode or cathode. This RESULTS in a reduction of corrosion kinetics.

Discussion

86.	Which of the following will act as cathode and anode respectively in a dry-cell battery?(a) Zinc and carbon(b) Carbon and zinc(c) Magnesium and zinc(d) Zinc and ammonium chlorideThe question was asked in an interview for internship.I would like to ask this question from Eight Forms topic in section Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct choice is (B) CARBON and zinc For EXPLANATION: Battery is a combination of cells in which chemical energy is converted into electrical energy. Carbon (noble electrode) ACTS as cathode and zinc (active electrode) acts as an anode. Moist ammonium chloride is used as an electrolyte.

Discussion

87.	What is/are the preventions of uniform corrosion?(a) Proper material coatings(b) Inhibitors(c) Cathodic protection(d) Proper material coatings, inhibitors, and cathodic protectionThe question was asked in an interview for internship.My doubt stems from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Right OPTION is (d) Proper material coatings, inhibitors, and CATHODIC protection To elaborate: Uniform CORROSION can be prevented by proper material coatings, inhibitors, and cathodic protection. Proper material coatings minimize the EXPOSURE area of metal. An inhibitor is a chemical substance that decreases the corrosion rate of metal by modifying the surface of anode or CATHODE.

Discussion

88.	What is the abbreviation of KLA regarding intergranular corrosion?(a) Knife-Line Attack(b) Knight-Line Attack(c) Knife-Life Action(d) Knight-Life ActionI have been asked this question in a national level competition.The question is from Eight Forms in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct answer is (a) Knife-Line ATTACK Explanation: KLA is abbreviated as Knife-Line Attack. Knife-Line Attack is similar to weld DECAY in that they both RESULTS from intergranular CORROSION and both are associated with welding.

Discussion

89.	What is the molecular formula of chromium carbide formed due to the depletion of chromium in 18-8 stainless steel?(a) Cr3C(b) Cr5C3(c) CrC(d) Cr23C6This question was posed to me by my college professor while I was bunking the class.My enquiry is from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» Right answer is (d) Cr23C6 To elaborate: Intergranular CORROSION in 18-8 stainless steel is DUE to the depletion of CHROMIUM content at the GRAIN boundary. This results in the formation of chromium carbide (Cr23C6) at the grain boundary. Chromium depleted zone is highly PRONE to corrosion and it is known as intergranular corrosion.

Discussion

90.	Which of the following chemical reaction that usually occurs in the crevice?(a) M^++H2O=MOH(b) M^++Cl^–=MCl(s)(c) M^+Cl^–+H2O=MOH(aq)+H^+Cl^–(d) 4OH^–=O2+2H2O+4e^–I have been asked this question by my school teacher while I was bunking the class.My doubt is from Eight Forms topic in division Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct CHOICE is (C) M^+Cl^–+H2O=MOH(aq)+H^+Cl^– Explanation: As the metallic ion concentration increases in the crevice, the migration of chloride IONS takes place to neutralize that. After that, METAL chlorides undergo hydrolysis and RESULTS in the formation of insoluble metal hydroxide and free acid.

Discussion

91.	Which of the following metal is highly prone to pitting corrosion?(a) 18-8 stainless steel by sulfuric acid with FeCl3(b) Titanium by sulfuric acid with FeCl3(c) Nickel by sulfuric acid with FeCl3(d) Copper by sulfuric acid with FeCl3I have been asked this question during a job interview.I need to ask this question from Eight Forms in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The CORRECT OPTION is (a) 18-8 stainless steel by sulfuric acid with FeCl3 To explain: Pitting is one of the most destructive and insidious FORMS of corrosion. 18-8 stainless steel is highly PRONE to pitting corrosion by sulfuric acid in the presence of FeCl3. Whereas other metals are relatively resistant to pitting. Because it mainly depends on oxide film for its corrosion-resistant.

Discussion

92.	What is the percent of zinc that consists of common yellow brass?(a) 70%(b) 30%(c) 40%(d) 60%I got this question at a job interview.I'm obligated to ask this question of Eight Forms in section Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct option is (b) 30% The explanation is: The COMPOSITION of common yellow BRASS is approximately 30% zinc and 70% copper. Dezincification alloy assumes a red or copper color that contracts to the original yellow color.

Discussion

93.	Metals or alloys that depend on oxide films for corrosive resistance are highly susceptible to crevice corrosion.(a) True(b) FalseThe question was posed to me in a job interview.This is a very interesting question from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct choice is (a) True Best explanation: Metals or ALLOYS that depend on oxide films for corrosive RESISTANCE are HIGHLY susceptible to crevice corrosion. These passive films are DESTROYED by high concentrations of hydrogen and chloride ions, and the metallic dissolution increases rapidly.

Discussion

94.	Define the distance effect regarding galvanic corrosion?(a) Corrosion occurs only at the junction of two metals(b) Corrosion occurs only at the edges of two metals(c) Corrosion decreases with increase in distance from the junction(d) Corrosion increases with increase in distance from the junctionThis question was addressed to me in an online quiz.My question is based upon Eight Forms in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct option is (c) CORROSION decreases with increase in distance from the junction Explanation: The galvanic effect is the POTENTIAL difference FORMED between two or more metals at its junction. It decreases on moving AWAY from the junction. Hence corrosion decreases with an increase in distance from the junction.

Discussion

95.	Which of the following type of brasses is/are highly prone to the uniform or layer-type dezincification?(a) Low brasses(b) High brasses(c) Low and high brasses(d) Neither high nor low brassesThis question was addressed to me in an interview for job.The doubt is from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT choice is (b) High BRASSES To elaborate: The composition of high brasses is usually 65% copper and 35% zinc. High brasses are highly prone to the UNIFORM or layer-type dezincification in ACIDIC environments.

Discussion

96.	Which of the following is/are the preventions of dezincification?(a) Minimizing oxygen concentration(b) Use of less susceptible alloy(c) Adding a small amount of arsenic, antimony(d) Removal of oxygen concentration, use of less susceptible alloy and adding a small amount of arsenic, antimonyI got this question in an online quiz.Question is from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering
Answer» Correct OPTION is (d) REMOVAL of oxygen concentration, use of less SUSCEPTIBLE alloy and adding a small amount of arsenic, antimony Easiest explanation: Dezincification can be minimized or reduced by i. Minimizing the oxygen concentration in the environment ii. Use of less susceptible alloy such as red BRASS (15% zinc) iii. Adding small amounts of arsenic, antimony, and phosphorus as an inhibitor

Discussion

97.	Which of the following is/are the characteristics of dezincified brass alloy?(a) Weak(b) Permeable(c) Porous(d) Weak, permeable and porousThis question was posed to me in an interview.Origin of the question is Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT choice is (d) Weak, PERMEABLE and porous Best EXPLANATION: Dezincified brass ALLOY is an alloy in which the zinc is REMOVED in a particular corrosive solution by selective leaching. Weak, permeable, and porous are the characteristics of dezincified brass alloy.

Discussion

98.	The incubation period is the amount of time required to initiate crevice corrosion on a corrosive site.(a) True(b) FalseI have been asked this question in an online interview.The query is from Eight Forms topic in division Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct option is (a) True The EXPLANATION is: The incubation PERIOD is the TIME required to initiate the crevice corrosion on a corrosive site. It depends on many factors such as i. Type of crevice formed ii. Nature of material used iii. Temperature iv. The DIFFERENCE in the concentration of oxygen in the crevice and its surroundings

Discussion

99.	Which of the following is the driving force in galvanic corrosion?(a) Conductivity of electrolyte(b) Crystal structure of metals(c) The potential difference between the two metals(d) Temperature of electrolyteI got this question during an interview for a job.This intriguing question originated from Eight Forms topic in chapter Eight Forms of Corrosion of Corrosion Engineering
Answer» The correct OPTION is (c) The potential difference between the two METALS To EXPLAIN I WOULD say: The principle driving force for current transfer and corrosion is the potential developed between the two metals. This potential difference can be altered by various factors such as conductivity of electrolyte and TEMPERATURE of the electrolyte.

Discussion

100.	Which of the following is/are the characteristics of the Knife-line attack?(a) KLA occurs immediately adjacent to the weld(b) KLA occurs in the stabilized steels only(c) KLA occurs in the non-stabilized steels only(d) KLA occurs in the stabilized steels and it occurs immediately adjacent to the weldThe question was asked by my college professor while I was bunking the class.Query is from Eight Forms in division Eight Forms of Corrosion of Corrosion Engineering
Answer» RIGHT choice is (d) KLA OCCURS in the stabilized steels and it occurs immediately ADJACENT to the weld Easiest explanation: KLA occurs in a NARROW band in the parent metal adjacent to weld and it occurs in the stabilized steels that are alloyed with niobium, titanium, and COLUMBIUM.

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