and answers with solutions 2025
Describe Passivation - ANSWER Passivation is the formation of a protective oxide film on the surface
reducing its chemical activity and its ability to corrode.
Describe the following factors and how they affect corrosion: - ANSWER • Oxygen: Oxygen increases the
rate of corrosion.
• Temperature: Corrosion usually accelerated with increasing temperature
• Chemical Salts: Increase the rate of corrosion by increasing the efficiency of the electrolyte.
• Humidity (or Wetness): The wetter the environment, the more corrosion is likely to occur.
• Pollutants and Acid Gases: Acid rain, chemical byproducts and chlorides all promote corrosion.
Two broad categories of corrosion can be described as: - ANSWER General
Localized
Describe Galvanic Corrosion - ANSWER Galvanic corrosion is an electrochemical action of two dissimilar
metals in the presence of an electrolyte and an electron conductive path, which occurs when dissimilar
metals come into contact.
Describe Cathodic Protection - ANSWER Cathodic protection is the reduction or elimination of corrosion
by making the structure to be protected a cathode by means of an impressed current or attachment to a
galvanic anode.
The two primary types of cathodic protection are: - ANSWER Impressed Current
Galvanic (Sacrificial)
Impressed current power sources include: - ANSWER Rectified commercial power
Solar cells
Generators
Fuel cells
,Wind-powered cells
Thermoelectric cells
Describe Cathodic Disbondment - ANSWER Cathodic disbondment is the separation of the coating from
the surface through hydroxyl (OH-) formation due to increased (made more negative) potential.
The principal component of mild carbon steel is - ANSWER A. Iron (Fe)
The formation of a thin surface layer on metals, whether an oxide, carbonate, or other compound, that
slows the rate of the corrosion process is called? - ANSWER D. Passivation
Which is the part of a corrosion cell where metal dissolves? - ANSWER A. Anode
Which of these elements is likely to accelerate corrosion on a steel structure? - ANSWER A. Salts
C. High temperatures
D. Pollutants
In a cathodic protection system the metal being protected is the? - ANSWER B. Cathode
When parts of a metal surface are shielded from full exposure to the environment because of the close
proximity of another metal, corrosion at that location is identified as? - ANSWER D. Crevice corrosion
Cathodic protection using impressed current is most commonly used on? - ANSWER C. Pipelines
Impressed current systems anodes include? - ANSWER A. Graphite
C. High silicon cast iron
Describe dehumidification: - ANSWER Dehumidification is the process of removing moisture vapor from
the air to lower its dew point.
,When planning enclosures, the following minimum requirements should be considered: - ANSWER •
Must be large enough to contain the whole work area.
• Not be larger than the performance capabilities of the dehumidification equipment.
• Be sturdy enough to hold up to intended work activities, potential loads, and possible inclement
weather.
• Have minimal leakage to maintain proper environmental conditions and ensure the dehumidification
system operates efficiently.
Describe air turns (air changes): - ANSWER • The air turnover principle eliminates air stratification, or
layering, in large open spaces by
recirculating the hot air that becomes trapped in the higher spaces
• The number of times it does this per hour is called air turns.
At and below what relative humidity does corrosion virtually cease? - ANSWER 0.4
Describe two ways to reduce the relative humidity of the boundary layer: - ANSWER • Increase the
surface temperature
• Reduce moisture content by dehumidification.
Types of dehumidification equipment include: - ANSWER • Refrigeration and desiccant
Describe several benefits of dehumidification: - ANSWER • Dries the air. Lowers the dew point. Permits
blasting the entire surface. Holds the blast with dry air. Helps in cleaning the surface. Holds the surface
during coating application.
You are the coating inspector on a project with dehumidification provided by a rotating bed type
dehumidifier. The silica gel has become contaminated. What do you expect to happen with the silica gel?
- ANSWER D. It can no longer adsorb moisture
What effect does the rotating bed dehumidifier have on the treated ambient air? - ANSWER B. It is
heated and the humidity decreases
, Some general basic centrifugal blast setups include: - ANSWER Tumbling Mill
Multi Table
Plain Table
Swing Table
Custom designed systems
Centrifugal blasting conveyor systems are commonly used for cleaning of: - ANSWER Plate
Rolled structural shapes
Large trusses
Girders
Portable centrifugal blasting systems can be used on: - ANSWER Ship decks, hull sides, and bottoms
Storage tanks
Concrete floors
Highways and bridge decks
Generally centrifugal blast systems are composed of the following elements: - ANSWER Centrifugal
abrasive throwing wheel
The blast cabinet (or enclosure)
In fixed systems, some type of material handling system
Abrasive recycling system
A dust collector and vent-pipe system
Abrasives
The efficiency of the centrifugal blast wheel(s) depends on several factors. - ANSWER Abrasive operating
mix
Size of the abrasive
Velocity of the abrasive coming off the wheel
Quantity and direction of the thrown abrasive
Condition of the feed parts