Passivation is the formation of a protective oxide Film on
Describe passivation the surface reducing its chemical activity and its ability to
corrode
Oxygen: oxygen increases the rate of corrosion
temperature
Temperature: corrosion usually accelerated with
Describe the following increasing temperature
factors and how they affect Chemical salts: increase the rate of corrosion by
corrosion increasing the efficiency of the electrolyte
humidity: the wetter the environment, the more
corrosion is likely to occur pollutants and acid gases: all
promote corrosion
Two broad categories of General and localized
corrosion can be described
as
Galvanic corrosion is an electrochemical action of two
dissimilar metals in the presence of an electrolyte and an
Describe galvanic corrosion
electron conductive path, Which occurs when the
dissimilar metals come into contact
Cathodic protection is the reduction or elimination of
Describe cathodic corrosion by making the structure to be protected a
protection cathode by means of impressed current or attachment
to a galvanic anode
The two primary types of Impressed current and galvanic (sacrificial)
cathodic protection are
1. Generators 2. Fuel cells 3. Wind powered cells 4.
impressed current power
Thermoelectric cells 5. Rectified commercial power 6.
sources include:
Solar Cells
, The separation of the coating from the surface through
Describe cathodic
hydroxyl formation due to increased ( made more
disbondment
negative ) potential.
Dehumidification is the process of removing moisture
Describe dehumidification
vapor from the air to lower its dew point
Must be large enough to contain the whole work area.
Not be larger than the performance capabilities of the
When planning enclosures dehumidification equipment.
the following minimum Be sturdy enough to hold up to intended work activities,
requirements should be potential loads, and a possible inclement weather.
considered Have minimal leakage to maintain proper environmental
conditions and ensure the dehumidification system
operates efficiently.
The air turnover principal illuminates air stratification, or
layering, in large open spaces by recirculating the hot air
Describe air turns (air
that becomes trapped in the higher spaces.
changes)
The number of times it does this per hour is called air
turns.
At & below what relative 40%
humidity does corrosion
virtually cease
Describe two ways to Increase the surface temperature and reduce moisture
reduce the relative humidity content by dehumidification
of the boundary layer
Types of dehumidification Refrigeration and desiccant
equipment include
Dries the air. Lowers the dew point. Permits blasting the
Describe several benefits of entire surface. Holds the blast with dry air. Helps in
dehumidification cleaning the surface. Holds the surface during coating
application.
Electronic hygrometers can Relative humidity, air temperature, and dewpoint
be used to determine temperature.
, Advanced environmental USB, IR, Bluetooth
testing instruments have the
ability to store data that can
be transferred to a
computer and other
devices. Transfer methods
include
Some general basic Tumbling mill, multitable, plain table, swing table, custom
centrifugal blast set ups designed systems
include
Centrifugal blasting Plate, rolled structural shapes, large trusses, girders
conveyor systems are
commonly used for
cleaning
Portable centrifugal Ship decks, hull sides, and bottoms. Storage tanks.
blasting systems can be Concrete floors. Highways and bridge decks.
used on
Centrifugal abrasive throwing wheel, the blast cabinet, in
Generally centrifugal blast
fixed systems some type of material handling system,
systems are composed of
abrasive recycling system, a dust collector and vent pipe
the following elements
system, abrasives.
Abrasive operating mix, size of the abrasive, velocity of
The efficiency of the
the abrasive coming off the wheel, quantity and
centrifugal blast wheels
direction of the thrown abrasive, condition of the feed
depends on several factors
parts.
Little amperage readings on An abrasive starved wheel, a flooded or choked wheel
a centrifugal blasting
machine could signify
To control the sizing of the abrasive mix, to remove sand,
The functions of the
spent abrasives, rust, dirt, and any other contaminants
centrifugal blasting
from the abrasive stream, to control abrasive
machine separator include
consumption
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