Types of corrosion MCQs With Answer

Introduction: Understanding types of corrosion MCQs with answer is essential for B. Pharm students involved in pharmaceutical manufacturing, storage, and material selection. This concise guide explores corrosion types such as uniform, galvanic, pitting, crevice, stress corrosion cracking, and microbiologically influenced corrosion, emphasizing mechanisms, influencing factors, testing methods, and prevention strategies like passivation, coatings, inhibitors, and cathodic protection. Mastering corrosion concepts helps ensure drug stability, container compatibility, and safe facility design. The following MCQs are designed to deepen comprehension of electrochemical principles, material behaviour, and practical mitigation used in pharmaceutical contexts. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary driving force behind most types of corrosion?

• Mechanical stress
• Electrochemical potential difference
• Thermal expansion
• Microbial growth

Correct Answer: Electrochemical potential difference

Q2. Which type of corrosion results in a uniform loss of material across the entire exposed surface?

• Pitting corrosion
• Galvanic corrosion
• Uniform corrosion
• Crevice corrosion

Correct Answer: Uniform corrosion

Q3. Pitting corrosion is especially dangerous because it:

• Produces uniform thinning that is easy to detect
• Creates small deep cavities leading to sudden failure
• Only affects non-metallic materials
• Is reversible with simple cleaning

Correct Answer: Creates small deep cavities leading to sudden failure

Q4. Galvanic corrosion occurs when:

• Two dissimilar metals are electrically connected in a corrosive electrolyte
• A single metal is exposed to air
• Only organic coatings degrade
• Temperature is decreased below freezing

Correct Answer: Two dissimilar metals are electrically connected in a corrosive electrolyte

Q5. Which metal becomes the anode in a galvanic couple?

• The more noble metal
• The less noble (more active) metal
• The metal with greater thickness
• The one coated with paint

Correct Answer: The less noble (more active) metal

Q6. Crevice corrosion typically occurs in which location?

• Open, well-aerated surfaces
• Shallow scratches on polished surfaces
• Confined spaces where stagnant electrolyte accumulates
• Regions under heavy mechanical load only

Correct Answer: Confined spaces where stagnant electrolyte accumulates

Q7. Stress corrosion cracking (SCC) requires which three elements to occur?

• Heat, cold, and light
• Mechanical stress, susceptible material, and corrosive environment
• Only high tensile stress and UV radiation
• Microbial presence, pH above 10, and oxygen

Correct Answer: Mechanical stress, susceptible material, and corrosive environment

Q8. Microbiologically influenced corrosion (MIC) is primarily driven by:

• Electrochemical potential only
• Bacterial or microbial metabolic activities altering local chemistry
• Mechanical abrasion from solids
• High temperature oxidation exclusively

Correct Answer: Bacterial or microbial metabolic activities altering local chemistry

Q9. Which of the following best describes passivation?

• Intentional removal of a protective oxide layer
• Formation of a thin protective oxide layer that inhibits corrosion
• Rapid breakdown of metal by acids
• A type of microbial corrosion

Correct Answer: Formation of a thin protective oxide layer that inhibits corrosion

Q10. Which test provides a rapid electrochemical measurement of corrosion tendency using current and potential behavior?

• Tafel polarization and potentiodynamic polarization
• Visual inspection only
• Hardness testing
• Tensile testing

Correct Answer: Tafel polarization and potentiodynamic polarization

Q11. In an electrochemical cell causing corrosion, the anodic reaction typically involves:

• Reduction of oxygen
• Oxidation of metal atoms to ions
• Precipitation of salts
• Formation of protective polymer films

Correct Answer: Oxidation of metal atoms to ions

Q12. The Nernst equation is used to:

• Calculate tensile strength
• Relate electrode potential to concentrations of oxidized and reduced species
• Determine melting point
• Measure pH directly

Correct Answer: Relate electrode potential to concentrations of oxidized and reduced species

Q13. Which of the following conditions increases the risk of pitting in stainless steels?

• Presence of chloride ions
• High pH alkaline solutions only
• Pure water with no ions
• High phosphate concentration preventing localized attack

Correct Answer: Presence of chloride ions

Q14. A material that forms a stable oxide layer and resists localized corrosion is termed:

• Active metal
• Passivated metal
• Cathodic metal
• Porous metal

Correct Answer: Passivated metal

Q15. In galvanic corrosion protection, a sacrificial anode is chosen to be:

• More noble than the protected metal
• Less noble (more active) than the protected metal
• Electrically insulating
• Non-conductive and inert

Correct Answer: Less noble (more active) than the protected metal

Q16. Cathodic protection works by:

• Making the protected metal the cathode to suppress anodic dissolution
• Increasing the anodic area of the structure
• Heating the metal surface
• Applying organic solvents to dissolve oxides

Correct Answer: Making the protected metal the cathode to suppress anodic dissolution

Q17. Erosion-corrosion differs from pure chemical corrosion because it involves:

• Only chemical attack in static conditions
• Mechanical removal of protective films combined with chemical attack
• Microbial action exclusively
• High-temperature oxidation only

Correct Answer: Mechanical removal of protective films combined with chemical attack

Q18. Which of the following is a common corrosion inhibitor used to protect metals in acidic cleaning solutions?

• Chromate compounds
• Sodium chloride
• Hydrochloric acid
• Ferrous sulfate

Correct Answer: Chromate compounds

Q19. The Pourbaix diagram (E-pH) helps predict:

• Mechanical fracture toughness
• Stable forms of an element (immune, passive, corroding) as a function of pH and potential
• Thermal conductivity variations
• Dielectric constant of materials

Correct Answer: Stable forms of an element (immune, passive, corroding) as a function of pH and potential

Q20. Which parameter directly quantifies the amount of metal lost to corrosion per unit area and time?

• Hardness
• Corrosion rate (e.g., mm/year or mpy)
• Electrical resistivity
• Thermal expansion coefficient

Correct Answer: Corrosion rate (e.g., mm/year or mpy)

Q21. Localized anodic dissolution surrounded by a cathodic area describes which corrosion form?

• Uniform corrosion
• Localized corrosion
• Ceramic degradation
• Hydrogen embrittlement

Correct Answer: Localized corrosion

Q22. Which metal commonly used for pharmaceutical equipment is chosen for corrosion resistance and cleanability?

• Plain carbon steel
• Stainless steel (e.g., 316L)
• Pure zinc
• Aluminum alloy 2024

Correct Answer: Stainless steel (e.g., 316L)

Q23. Which ion is most notorious for initiating localized attack on stainless steels?

• Nitrate
• Chloride
• Sulfate
• Phosphate

Correct Answer: Chloride

Q24. In electrochemical corrosion, the cathodic reaction in aerated neutral water typically is:

• Hydrogen evolution only
• Oxygen reduction
• Metal oxidation
• Chlorine evolution

Correct Answer: Oxygen reduction

Q25. Which design strategy reduces the risk of crevice corrosion in pharmaceutical tanks?

• Using narrow gaps and rough welds
• Designing smooth surfaces and avoiding stagnant crevices
• Increasing bolt count to create more joints
• Using overlapping flanges without sealants

Correct Answer: Designing smooth surfaces and avoiding stagnant crevices

Q26. Which analytical technique can map localized corrosion initiation sites on metal surfaces?

• Scanning electron microscopy (SEM)
• Ultraviolet spectroscopy for organics
• Gas chromatography
• X-ray diffraction for bulk crystal structure only

Correct Answer: Scanning electron microscopy (SEM)

Q27. Anodic protection is most effective for:

• Active metals like aluminum in all acids
• Passivable metals such as stainless steel in certain aggressive environments
• Non-conductive polymers
• Glassware used in labs

Correct Answer: Passivable metals such as stainless steel in certain aggressive environments

Q28. What role does oxygen concentration play in differential aeration cell corrosion?

• No role; oxygen has no effect
• Areas with lower oxygen become anodic and corrode
• Areas with higher oxygen always corrode
• Only temperature matters, not oxygen

Correct Answer: Areas with lower oxygen become anodic and corrode

Q29. Which of the following is a common sign of microbiologically influenced corrosion in pipelines?

• Uniform polishing of the interior surface
• Localized pitting with biofilm presence
• Complete absence of any deposits
• Only surface oxidation with no pitting

Correct Answer: Localized pitting with biofilm presence

Q30. Which parameter is directly measured in linear polarization resistance (LPR) to estimate corrosion rate?

• Electrical conductivity of the metal
• Polarization resistance (Rp)
• Mass loss after one year
• Optical absorption

Correct Answer: Polarization resistance (Rp)

Q31. Which alloying element improves resistance to pitting and crevice corrosion in stainless steels?

• Carbon
• Molybdenum
• Phosphorus
• Sulfur

Correct Answer: Molybdenum

Q32. Hydrogen embrittlement is a corrosion-related phenomenon where:

• Hydrogen reduces the electrical conductivity of metal
• Hydrogen enters metal lattice, causing loss of ductility and brittle failure
• Hydrogen always prevents corrosion
• Hydrogen only affects non-metals

Correct Answer: Hydrogen enters metal lattice, causing loss of ductility and brittle failure

Q33. Which surface treatment enhances passive film formation on stainless steel?

• Pickling and passivation with nitric acid
• Applying salt spray
• Leaving welding slag in place
• Coating with chloride-rich paint

Correct Answer: Pickling and passivation with nitric acid

Q34. Which unit is commonly used to express corrosion rate in pipelines and equipment?

• Megapascals
• Millimeters per year (mm/year) or mils per year (mpy)
• Candela
• Watts per meter

Correct Answer: Millimeters per year (mm/year) or mils per year (mpy)

Q35. Which factor does NOT significantly influence corrosion in pharmaceutical environments?

• pH of cleaning and process solutions
• Temperature and exposure duration
• Electrochemical properties of materials
• Color of the storage room walls

Correct Answer: Color of the storage room walls

Q36. How does chloride concentration typically affect corrosion rate of stainless steels?

• Lower chloride always increases corrosion resistance
• Higher chloride concentrations promote localized attack and increase corrosion risk
• Chlorides have no effect on stainless steels
• Chlorides form beneficial passivating layers

Correct Answer: Higher chloride concentrations promote localized attack and increase corrosion risk

Q37. Which method is commonly used in pharmaceutical industry to verify corrosion resistance of storage vessels?

• Taste testing of stored liquids
• Scheduled visual inspections and periodic corrosion testing (e.g., coupon tests)
• Measuring electromagnetic emissions
• Assessing color changes in room lighting

Correct Answer: Scheduled visual inspections and periodic corrosion testing (e.g., coupon tests)

Q38. In the context of corrosion, “anodic area effect” refers to:

• Larger anodic area always reduces corrosion of the anode
• Small anodic area relative to cathodic area intensifies corrosion of the anode
• Area has no impact on galvanic corrosion
• Only cathodic area matters

Correct Answer: Small anodic area relative to cathodic area intensifies corrosion of the anode

Q39. Which of the following coatings provides a physical barrier and chemical resistance for metal surfaces?

• Organic polymer coatings (e.g., epoxy)
• Salt deposition
• Loose rust layers
• Thin water film only

Correct Answer: Organic polymer coatings (e.g., epoxy)

Q40. Which electrochemical term describes the potential at which anodic and cathodic currents are equal for a corroding metal?

• Open circuit potential or corrosion potential (Ecorr)
• Breakdown potential only
• Standard hydrogen potential always
• Thermal potential

Correct Answer: Open circuit potential or corrosion potential (Ecorr)

Q41. Which practice minimizes galvanic corrosion when joining dissimilar metals in pharmaceutical equipment?

• Direct metal-to-metal contact with no insulation
• Electrically insulating gaskets or coatings between dissimilar metals
• Using the thinnest possible sacrificial layer
• Increasing surface roughness at the joint

Correct Answer: Electrically insulating gaskets or coatings between dissimilar metals

Q42. Which phenomenon occurs when chloride ions concentrate in a crevice, lowering pH and promoting localized attack?

• Alkalization
• Acidification within crevice and localized corrosion
• Complete neutralization of ions
• Uniform passivation improvement

Correct Answer: Acidification within crevice and localized corrosion

Q43. A corrosion coupon is used to:

• Measure mechanical strength only
• Assess real-time corrosion rate by exposing a known metal sample to service conditions
• Seal a flange permanently
• Increase galvanic coupling

Correct Answer: Assess real-time corrosion rate by exposing a known metal sample to service conditions

Q44. Which type of corrosion is accelerated by fluctuating tensile stresses in the presence of a corrosive medium?

• Intergranular corrosion only
• Fatigue corrosion or corrosion fatigue
• Uniform corrosion under static load
• Chemical oxidation in absence of stress

Correct Answer: Fatigue corrosion or corrosion fatigue

Q45. Intergranular corrosion is most likely to occur when:

• Grain boundaries are depleted of protective alloying elements like chromium
• Grains are extremely fine and uniform
• The metal is fully annealed and homogeneous
• There is a continuous, intact passive film

Correct Answer: Grain boundaries are depleted of protective alloying elements like chromium

Q46. Which maintenance action helps reduce corrosion in pharmaceutical piping systems?

• Allowing long-term stagnant solution retention
• Regular flushing, cleaning, and avoiding dead legs
• Using low-quality welds
• Never applying protective coatings

Correct Answer: Regular flushing, cleaning, and avoiding dead legs

Q47. Which electrochemical measurement yields information on corrosion kinetics and Tafel slopes?

• Static weight measurement
• Potentiodynamic polarization (Tafel extrapolation)
• Optical microscopy only
• Gas chromatography

Correct Answer: Potentiodynamic polarization (Tafel extrapolation)

Q48. Which metal is most commonly used as a sacrificial anode for cathodic protection in marine environments?

• Gold
• Zinc, magnesium, or aluminum alloys
• Stainless steel
• Copper-nickel alloys

Correct Answer: Zinc, magnesium, or aluminum alloys

Q49. Which statement about corrosion monitoring in pharmaceutical plants is true?

• Monitoring is unnecessary if initial material selection was good
• Regular monitoring helps detect early corrosion, ensuring product safety and equipment longevity
• Only visual checks are sufficient for all corrosion types
• Monitoring should be limited to yearly inspections only

Correct Answer: Regular monitoring helps detect early corrosion, ensuring product safety and equipment longevity

Q50. Why is understanding corrosion important for B. Pharm students?

• It only affects mechanical engineers, not pharmacists
• Corrosion impacts drug container compatibility, product purity, and facility safety, influencing pharmaceutical quality
• Corrosion is only a cosmetic issue and irrelevant to pharmaceuticals
• It determines taste of drugs directly

Correct Answer: Corrosion impacts drug container compatibility, product purity, and facility safety, influencing pharmaceutical quality

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com