LEVEL 2 Flashcards
Describe Passivation
The production of a tightly adhered layer formed from the corrosion product (2.3 Definition Page 2-2/3)
Describe the following factors and how they affect corrosion (Oxygen, Temperature, Chemical Salts, Humidity, and Pollutants and acid gases)
Oxygen - Like water, oxygen increases the rate of corrosion. In oxygen-deficient environment corrosion rate and destruction of metal are much slower
Temperature - Accelerate with increased temperature
Chemical Salts - increase the rate of corrosion by increasing the conductivity of the electrolyte. The most common chemical is seawater, and salts disposed on steel can extract moisture from the air.
Humidity - The wetter the environment, the more likely corrosion is to occur. At 60% humidity decreases iron corrosion rates.
Pollutants and Acid Gases - can dissolve in a moisture film on the metal. these materials reduce electrical resistance in the electrolyte, increasing the corrosion rate.
(2.6 Corrosion Rate Factor Page 2-5/6)
Two broad categories of corrosion can be described as:
General and Localized Corrosion (2.7 Type of Corrosion) Page 2-6:9
Describe galvanic corrosion
Is the electrochemical action of two dissimilar metals in contact in the presence of an electrolyte, and an electron conductive path. The more reactive metals corrode to protect the more noble metals. (2.7.4 Galvanic Corrosion Page 2-9)
Describe cathodic protection
reduces or eliminates corrosion by turning the protected structure into a cathode by either an impressed current or attachment to a galvanic anode (2.8.1 Cathodic Protection Definition Page 2-10)
The two primary types of cathodic protection are:
Galvanic and Impressed Current. (Section 2.8.3 Page 2-11:10)
Impressed current power sources include:
Rectified commercial power, Solar cells, generators, fuel cells, wind-powered cells, and thermoelectric cells (Section 2.8.4.2 Page 2-13)
Describe cathodic disbondment:
separation of the coating from the surface from an increase in the voltage (potential) (Section 2.8.4.3.2 Cathodic Disbondment Page 2-14)
Electronic Hygrometers determines
Surface and Air temperature, Relative Humidity, Dew point, Delta T, Wet and Dry Bulb temperature (Section 4.2 Digital Electronic Hygrometers Page 4-1:3)
Advanced environmental testing instruments can store data that can be transferred to a computer and other devices. Transfer Methods:
USB, IR(Printer), and Bluetooth. (Section 4.4 Advanced Data Collection Methods Page 4-7)
In general, basic centrifugal blast setups include:
Tumbling mills, Multi-table machines, Plain table machines, swing tables, and custom-designed systems (Section 6.1 Introduction Page 6-1:5)
Centrifugal blast conveyor systems are commonly used for cleaning:
Prefabrication cleaning of plates, rolled structural shapes, large trusses, girders, and other large structural parts. (Section 6.1 Introduction Page 6-1:5)
Portable centrifugal blasting systems can be used:
Ship decks, hull sides, bottoms, storage tanks, concrete floors, highway, and bridge decks. (Section 6.2 Portable and remote operated systems Page 6-5)
Generally, centrifugal blast systems are composed of the following elements:
abrasive throwing wheel, blast cabinet, recycling systems, dust collector, and abrasives
The efficiency of the centrifugal blast wheels depends on several factors:
Abrasive operating mix, size of the abrasive, velocity of the abrasive, quantity and direction of the thrown abrasive, and condition of the feed parts (Section 6.2.2 Blast Wheel Page 6-7)
