Worksheetscorrosion
Total questions: 30
Worksheet time: 15mins
Which factor primarily distinguishes wet, moist, and dry atmospheric corrosion?
Temperature
Oxygen concentration
Degree of surface moisture
Presence of pollutants
Wet atmospheric corrosion occurs when:
No moisture is present on the metal surface
An invisible film of adsorbed moisture exists
A visible liquid film of water is present and humidity is close to 100%
The temperature exceeds 400°C
The invisible film responsible for moist atmospheric corrosion forms mainly due to:
Mechanical erosion
Capillary adsorption or chemical condensation
Surface oxidation at high temperature
UV radiation
Which statement best describes the corrosion rate as a function of moisture film thickness?
It increases linearly with increasing moisture thickness
It decreases continuously with increasing moisture thickness
It is constant regardless of moisture conditions
It reaches zero when dry, peaks at intermediate moisture, then decreases in fully wet conditions
Which stage of biofilm development typically has a thickness of 1-50 um?
Mature stage
Developing stage
Initial stage
Final degradation stage
Which type of atmospheric corrosion dominates when the metal surface is completely free of moisture?
Dry atmospheric corrosion
Wet atmospheric corrosion
Moist atmospheric corrosion
Crevice corrosion
What property makes aluminum alloys highly heat-resistant at 400-450°C?
High electrical conductivity
Formation of stable protective oxide layers
Their ability to absorb moisture
Their low melting temperature
How is corrosion best defined?
A process that strengthens metals when exposed to the environment
The natural degradation of metals caused by chemical or physicochemical interactions
The application of protective coatings to metals
The mixing of oil products with water
Which form of corrosion is most frequently observed in oil refining operations?
Crevice-type corrosion
CO2-related corrosion (sweet corrosion)
Erosion-driven corrosion
Corrosion triggeres microorganisms
Hydrogen sulfide (HS) becomes strongly corrosive when:
Pressure is high
Oxygen is present
Water is available
Nitrogen is released
Which corrosion mechanism results from microbial processes?
Corrosion caused by fluid erosion
Microbiologically influenced corrosion (MIC)
CO2-induced corrosion
Corrosion occurring in narrow gaps
Which substance in crude oil leads to sulfidation?
Nitrogen-based compounds
Heavy organic resins
Sulfur-containing species including H2S
Phosphate compounds
Which emulsion type shows higher corrosive potential?
Water dispersed in oil (W/O)
Oil dispersed in water (OW)
Both emulsions cause equal corrosion
Neither emulsion increases corrosion
What does the emulsion inversion point (EIP) represent?
The stage at which water fully evaporates
The changeover from W/O to O/W structure
The time needed for the breakdown of the emulsion film
The temperature where corrosion initiates
Which orientation of a metal surface is generally most susceptible to corrosion?
Vertical placement
Inclined positioning
Horizontal placement
Ceramic surfaces
Which option below does not help reduce corrosion?
Removing salts from crude oil
Adding corrosion-inhibiting chemicals
Raising the salt concentration in crude
Selecting proper construction materials
Why is ammonia (NH) injected into refinery systems?
To raise the acidity level
To neutralize hydrochloric acid and control corrosion
To speed up metal oxidation
To increase emulsions
What factors influence sweet corrosion in the refining industry?
Water content, CO, concentration, temperature, and pH
Presence of sulfur bacteria only
Ultraviolet light exposure
High oxygen content exclusively
Why is sweet corrosion considered the most prevalent form of corrosion in refining operations?
CO, is commonly present in petroleum and water systems
It occurs only at high temperatures
It requires bacteria to initiate the process
It only happens in stainless steel
Which gas becomes a highly corrosive agent only in the presence of water, leading to pipeline embrittlement?
Carbon dioxide (CO2)
Hydrogen sulfide (HS)
Nitrogen (N2)
Methane (CHa)
What is the typical thickness of a biofilm in the developing (maturing) stage?
1-10 um
50-500 um
0.5-2 mm
What type of corrosion typically occurs in narrow gaps or crevices?
Uniform corrosion
Crevice corrosion
Stress corrosion cracking
Sweet corrosion
What is the primary mechanism by which erosion corrosion increases corrosion reaction rate?
Increasing oxygen concentration in stagnant water
Removing the protective passive layer from the metal surface
Reducing CO, solubility
Lowering temperature in the pipeline
How does erosion corrosion affect the passive layer on the pipe wall?
Strengthens it
Reduces its thickness and exposes bare metal
Converts it to a non-reactive oxide
Has no effect
Which type of corrosion is driven by bacterial activity?
Erosion corrosion
Microbiologically induced corrosion (MIC)
Sweet corrosion
Galvanic corrosion
What corrosive byproducts are produced by bacteria in microbiologically induced corrosion (MIC)?
Sulfides, organic acids, and CO2
Oxygen and nitrogen
Sodium chloride and potassium hydroxide
Hydrogen and methane
How do waste products like CO2, H2S, and organic acids contribute to MIC?
They inhibit bacterial growth
They increase local acidity, accelerate corrosion, and attack metal surfaces
They form a protective layer on the pipe
They neutralize water hardness
Which statement best describes the role of biofilms in MIC?
Biofilms always accelerate corrosion due to increased microbial density
Biofilms uniformly protect the metal surface from oxygen penetration
Biofilms create micro-environments that can either increase or decrease corrosion
Biofilms act only as physical barriers without chemical influence
Which group of microorganisms is primarily responsible for producing hydrogen sulfide, a key driver of MIC in oil and gas facilities?
Acid-producing bacteria (APB)
Sulfate-reducing bacteria (SRB)
Sulfur-oxidizing bacteria (SOB)
Methane-oxidizing bacteria
What specific environmental condition makes HS transform from non-corrosive to highly corrosive in sour corrosion?
Presence of water or moisture
High oxygen content
Low temperature
Alkaline pH conditions
