Prevention of corrosion MCQs With Answer

Prevention of corrosion MCQs With Answer is an essential revision resource for B.Pharm students studying material compatibility, equipment longevity, and drug quality control. This introduction covers corrosion mechanisms, electrochemical concepts, common forms like pitting and galvanic corrosion, and practical prevention strategies such as material selection, coatings, passivation, cathodic protection, and corrosion inhibitors. Emphasis is on pharmaceutical equipment (stainless steels, welds, cleaning) and monitoring techniques (polarization, EIS) that affect product safety and regulatory compliance. SEO-rich keywords include prevention of corrosion MCQs with answer, corrosion inhibitors, cathodic protection, pitting corrosion, and pharmaceutical corrosion control. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is the primary electrochemical process responsible for most forms of metallic corrosion?

• Physical abrasion
• Oxidation-reduction (redox) reactions
• Thermal expansion
• Microbial deposition

Correct Answer: Oxidation-reduction (redox) reactions

Q2. Which type of corrosion is characterized by localized holes or pits on a metal surface?

• Uniform corrosion
• Galvanic corrosion
• Pitting corrosion
• Intergranular corrosion

Correct Answer: Pitting corrosion

Q3. Which stainless steel grade is most commonly recommended for pharmaceutical equipment exposed to chlorides?

• 304
• 316L
• 410
• 201

Correct Answer: 316L

Q4. What role do corrosion inhibitors play in preventing corrosion in pharmaceutical systems?

• Increase surface roughness
• Form a protective film or block electrochemical reactions
• Raise operating temperature
• Promote galvanic coupling

Correct Answer: Form a protective film or block electrochemical reactions

Q5. Which mechanism describes galvanic corrosion?

• Uniform attack across a single metal
• Localized corrosion in crevices
• Coupling of two different metals causing the more anodic metal to corrode
• Corrosion only in high temperature environments

Correct Answer: Coupling of two different metals causing the more anodic metal to corrode

Q6. Passivation of stainless steel primarily involves formation of which protective film?

• Polymeric film
• Chromium oxide layer
• Iron sulfide scale
• Calcium carbonate deposit

Correct Answer: Chromium oxide layer

Q7. Which test measures electrochemical behavior to estimate corrosion rates by polarizing the metal slightly?

• Salt spray test
• Linear polarization resistance (LPR)
• Hardness test
• Visual inspection

Correct Answer: Linear polarization resistance (LPR)

Q8. What is crevice corrosion commonly associated with in pharmaceutical equipment?

• Highly polished surfaces only
• Areas with stagnant solution such as gasketed joints and threaded connections
• Entire tank uniformly
• Only high-temperature steam zones

Correct Answer: Areas with stagnant solution such as gasketed joints and threaded connections

Q9. Which of the following is a cathodic protection method?

• Applying a polymer coating
• Using sacrificial anodes (e.g., zinc)
• Increasing oxygen concentration
• Welding dissimilar metals

Correct Answer: Using sacrificial anodes (e.g., zinc)

Q10. Stress corrosion cracking (SCC) requires which combination to occur?

• Mechanical stress, susceptible material, and corrosive environment
• Only low pH environment
• High oxygen and no stress
• Purely microbial action

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

Q11. Which factor increases the rate of general corrosion in many metals?

• Lower temperature
• Presence of oxygen and moisture
• Complete absence of electrolytes
• High vacuum

Correct Answer: Presence of oxygen and moisture

Q12. What is the primary concern of corrosion in contact with pharmaceutical products?

• Only aesthetic appearance
• Contamination, leachables, and compromised product quality
• Reducing melting point of APIs
• Improving dissolution

Correct Answer: Contamination, leachables, and compromised product quality

Q13. Which coating type provides a barrier by physically separating metal from the environment?

• Conversion coating
• Barrier (polymeric) coating
• Galvanic coating that is anodic
• Noneffective thin film

Correct Answer: Barrier (polymeric) coating

Q14. Which ion commonly causes pitting in stainless steels?

• Sulfate (SO4^2-)
• Chloride (Cl^-)
• Carbonate (CO3^2-)
• Nitrate (NO3^-)

Correct Answer: Chloride (Cl^-)

Q15. What is the purpose of passivation treatments for stainless steel in pharma applications?

• Remove chromium from surface
• Enhance the formation of the protective oxide and remove free iron
• Increase surface roughness
• Make the surface more hydrophobic

Correct Answer: Enhance the formation of the protective oxide and remove free iron

Q16. Which analytical technique provides information on corrosion mechanisms via impedance measurements?

• Scanning electron microscopy (SEM)
• Electrochemical impedance spectroscopy (EIS)
• Gas chromatography (GC)
• Thermogravimetric analysis (TGA)

Correct Answer: Electrochemical impedance spectroscopy (EIS)

Q17. In galvanic series, the metal that corrodes preferentially is the one that is:

• Most noble
• More cathodic
• More anodic
• Coated with paint

Correct Answer: More anodic

Q18. What design consideration minimizes corrosion risk in piping systems?

• Creating dead legs and stagnant zones
• Ensuring good drainage and avoiding crevices
• Using mismatched dissimilar metals throughout
• Maximizing welded joints with sharp crevices

Correct Answer: Ensuring good drainage and avoiding crevices

Q19. Which of the following is a common chromate-free conversion coating used for corrosion protection?

• Zinc phosphate
• Lead chromate
• Mercury plating
• Arsenic oxide

Correct Answer: Zinc phosphate

Q20. Which monitoring technique is used for real-time corrosion rate measurement in plant?

• Periodic visual inspection only
• Online electrical resistance probes and LPR sensors
• Single-time destructive coupon test with no replacement
• Mass spectrometry of process fluid

Correct Answer: Online electrical resistance probes and LPR sensors

Q21. Which parameter is reduced by using properly formulated corrosion inhibitors in water systems?

• pH only
• Corrosion current density
• Surface area of metal
• Mechanical strength

Correct Answer: Corrosion current density

Q22. Which statement about sacrificial anodes is true?

• The anode is more noble than the protected metal
• The anode corrodes preferentially to protect the structure
• The anode prevents oxygen access mechanically
• Sacrificial anodes are ineffective in electrolyte contact

Correct Answer: The anode corrodes preferentially to protect the structure

Q23. What is the effect of high chloride concentration on passive films of stainless steel?

• It stabilizes the passive film
• It disrupts or breaks down the passive film causing localized attack
• It converts chromium oxide into a stronger barrier
• Chloride has no effect

Correct Answer: It disrupts or breaks down the passive film causing localized attack

Q24. In accelerated corrosion testing for pharma components, which method simulates harsh atmospheric conditions?

• Autoclave sterilization
• Salt spray (fog) testing
• High-performance liquid chromatography
• Dry heat aging only

Correct Answer: Salt spray (fog) testing

Q25. Which alloying element greatly improves stainless steel’s resistance to pitting?

• Nickel
• Chromium
• Manganese
• Lead

Correct Answer: Chromium

Q26. How does high-purity water used in pharma processes affect corrosion?

• Always prevents corrosion because it’s pure
• Can be aggressive due to low conductivity and dissolved gases, potentially increasing localized corrosion
• Causes immediate passivation of all metals
• Contains no effect since it lacks ions

Correct Answer: Can be aggressive due to low conductivity and dissolved gases, potentially increasing localized corrosion

Q27. Which maintenance practice reduces corrosion risk during steam sterilization cycles?

• Leaving residues and deposits inside equipment
• Regular cleaning, drying, and corrosion-resistant weld finishes
• Using incompatible gasket materials
• Using chlorinated cleansers without rinsing

Correct Answer: Regular cleaning, drying, and corrosion-resistant weld finishes

Q28. What is the main advantage of electropolishing stainless steel in pharma?

• Increases surface roughness for better adhesion
• Removes surface contaminants, reduces roughness, and enhances passivity
• Deposits a thick organic layer
• Introduces micro-crevices intentionally

Correct Answer: Removes surface contaminants, reduces roughness, and enhances passivity

Q29. Which regulatory concern is linked to corrosion in pharmaceutical manufacturing?

• Only energy efficiency
• Contamination from metal ions, leachables and extractables affecting product safety and GMP compliance
• Noise pollution
• Employee dress code

Correct Answer: Contamination from metal ions, leachables and extractables affecting product safety and GMP compliance

Q30. What is the likely outcome when two dissimilar metals are electrically connected in an electrolyte?

• No reaction occurs
• The less noble (more anodic) metal corrodes faster
• Both metals become immune to corrosion
• The more noble metal dissolves preferentially

Correct Answer: The less noble (more anodic) metal corrodes faster

Q31. Which practice reduces galvanic corrosion risk between stainless steel and carbon steel?

• Directly coupling them without insulation
• Insulating the junction or using compatible filler materials
• Using acidic cleaning agents to speed up corrosion
• Welding dissimilar metals without barrier

Correct Answer: Insulating the junction or using compatible filler materials

Q32. Which of the following is an anodic inhibitor mechanism?

• Increasing cathodic reaction rate
• Forming a passive oxide film that blocks anodic dissolution
• Providing sacrificial metal to corrode
• Raising solution temperature

Correct Answer: Forming a passive oxide film that blocks anodic dissolution

Q33. For corrosion calculation by weight loss, which additional parameter is essential besides mass loss?

• Color of metal
• Exposed surface area and exposure time
• Operator’s experience
• Type of lubricant used

Correct Answer: Exposed surface area and exposure time

Q34. Which is a common symptom of crevice corrosion?

• Uniform thinning across whole surface
• Localized attack adjacent to crevices with deposit of corrosion products
• Complete immunity of metal
• Only changes in magnetic properties

Correct Answer: Localized attack adjacent to crevices with deposit of corrosion products

Q35. Which cleaning practice can inadvertently promote corrosion if not properly followed?

• Neutral pH rinsing and complete drying
• Leaving residues of strong chlorinated cleaners and failing to rinse thoroughly
• Using deionized water rinse and drying
• Periodic inspection

Correct Answer: Leaving residues of strong chlorinated cleaners and failing to rinse thoroughly

Q36. Which instrument gives surface morphology information to evaluate corrosion pits microscopically?

• pH meter
• Scanning electron microscope (SEM)
• Ultraviolet spectrophotometer
• Thermometer

Correct Answer: Scanning electron microscope (SEM)

Q37. What is under-deposit corrosion?

• Corrosion that occurs uniformly in open surfaces
• Localized corrosion beneath deposits, scale, or biofilms where crevice-like conditions form
• Only occurs in dry air
• Corrosion prevented by the deposit

Correct Answer: Localized corrosion beneath deposits, scale, or biofilms where crevice-like conditions form

Q38. Which factor does NOT generally increase the risk of pitting on stainless steel?

• High chloride concentration
• Low oxygen content in stagnant crevices
• Smooth, polished surface with no contaminants
• Elevated temperature

Correct Answer: Smooth, polished surface with no contaminants

Q39. What is the primary function of a corrosion allowance in equipment design?

• Reduce weight of vessels
• Provide extra thickness so equipment remains safe despite expected material loss from corrosion
• Increase heat transfer efficiency
• Improve aesthetic appearance

Correct Answer: Provide extra thickness so equipment remains safe despite expected material loss from corrosion

Q40. Which gas dissolved in water accelerates corrosion of iron-based metals?

• Nitrogen
• Oxygen
• Argon
• Helium

Correct Answer: Oxygen

Q41. Which surface finish is generally preferred in pharma for minimizing corrosion and microbial buildup?

• Rough machined finish
• Electropolished smooth finish
• Deep etched finish
• Unpolished cast surface

Correct Answer: Electropolished smooth finish

Q42. Which is an effect of microbiologically influenced corrosion (MIC) in pharmaceutical systems?

• Only aesthetic change with no functional impact
• Localized accelerated corrosion, often associated with biofilms and sulfide production
• Guaranteed passivation of metal
• Improved product purity

Correct Answer: Localized accelerated corrosion, often associated with biofilms and sulfide production

Q43. Which protective strategy uses a more active metal to protect a structural metal in contact with electrolyte?

• Barrier coating
• Sacrificial anode cathodic protection
• Oxygen enrichment
• Increasing pH below 1

Correct Answer: Sacrificial anode cathodic protection

Q44. For pharmaceutical stainless steel surfaces, which cleaning validation parameter helps ensure corrosion control?

• Residue limits, pH of rinse, and absence of chloride residues
• Only visual sheen
• Amount of lubricant remaining
• Color of cleaning solution

Correct Answer: Residue limits, pH of rinse, and absence of chloride residues

Q45. Which of the following best describes anodic protection?

• Applying a protective coating that is inert
• Maintaining a metal at a stable passive potential by applying an external anodic current
• Using sacrificial anodes exclusively
• Adding oxygen to accelerate passivity loss

Correct Answer: Maintaining a metal at a stable passive potential by applying an external anodic current

Q46. Which parameter is used to express corrosion rate commonly in engineering?

• mg of material per hour only
• Millimeters per year (mm/year) or mils per year (mpy)
• Liters per minute
• Degrees Celsius

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

Q47. Which action is recommended when selecting materials for a pharma reactor handling acidic solutions?

• Select carbon steel without consideration
• Evaluate corrosion resistance of candidate alloys and consider linings or coatings
• Ignore compatibility if cost is lower
• Always use pure copper

Correct Answer: Evaluate corrosion resistance of candidate alloys and consider linings or coatings

Q48. Which analytical approach detects early localized corrosion by measuring tiny changes in current?

• Mass spectrometry
• Electrochemical noise and localized electrochemical techniques
• Thermal conductivity
• Simple weight estimation visually

Correct Answer: Electrochemical noise and localized electrochemical techniques

Q49. What is the effect of proper welding and post-weld cleaning on corrosion?

• Increases risk of intergranular and crevice corrosion due to residues if not done correctly; proper practices reduce corrosion
• Always causes more corrosion regardless of cleaning
• Has no effect on corrosion
• Makes metals immune to all forms of corrosion

Correct Answer: Increases risk of intergranular and crevice corrosion due to residues if not done correctly; proper practices reduce corrosion

Q50. Which documentation or standards are commonly referenced for corrosion control and testing in industry?

• ASTM, ISO, NACE standards and internal GMP protocols
• Only local weather reports
• Food recipes
• None; standards are unnecessary

Correct Answer: ASTM, ISO, NACE standards and internal GMP protocols

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