Corrosion
Terms
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- process of metals breaking down to their simpler natural state
- corrosion
- metal can be chemically broken down by...
- coming in contact with a corrosive liquid or gas
- moisture and contaminates on a metal surface can...
- activate and speed up the corrosion process
- two different types of metal making contact can corrode if...
- a liquid or vapor in present
- two types of metals that determine how fast corrosion will occur
- anodic and cathodic
- magnesium, aluminum, steel, chrome, and copper
- anodic metals
- greater tendency to corrode
- anodic metals
- stainless steel, titanium, gold and graphite
- cathodic metals
- lesser tendency to corrode
- cathodic metals
- buildup of corrosion at a metal-to-metal joint
- electrochemical corrosion
- four conditions required for electrochemical corrosion to occur
- anodic area, cathodic area, electrolyte, metal
- the atoms in a ____ metal give up electrons
- anodic
- dissimilar conductive material
- cathode
- must connect anode and cathode so that the ions can carry electric current between them
- electrolyte
- enables electrons to move from anodic, where they're released, to cathodic
- metal-to-metal (electrical) contact
- eliminating ___ will stop electrochemical corrosion
- any of the four conditions: anodic/cathodic area, electrolyte, metal
- ___ is present in the air and often contains contaminates that increase its corrosive effects.
- moisture
- corrosion increases as temperatures...
- rise
- warm, moist air tends to ___ corrosion
- accelerate
- present very serious threat of corrosion
- high humidity and air temps and dew points of 85°
- salt - laden air and topic conditions causes the corrosive environment to become
- extremely severe and may cause catastrophic equipment failure
- ome metals, such as stainless steel and titanium, produce corrosion products that are so tightly bound that they form...
- passive film
- an invisible layer of oxide that film prevents further corrosion
- passive film
- direct chemical or electrochemical attack on a metal surface characterized by a consistent cover of corrosion over a large surface area.
- uniform surface corrosion
- electrochemical and recognized by corrosion buildup at the joint between the metals
- galvanic corrosion
- producing a direct current of electricity
- galvanic reaction
- results in corrosion on the more active, or anodic, metal.
- galvanic reaction
- occur along the edges or between layers of extruded, rolled, wrought, and forged high-strength aluminum and magnesium parts
- Intergranular corrosion and exfoliation
- attack on the grain boundaries of metal
- Intergranular corrosion
- advanced form of Intergranular corrosion
- exfoliation
- four stages of corrosion prevention and control
- cleaning, inspection, control, protection
- first, and most important, step in preventing corrosion
- cleaning
- field personnel can prevent corrosion by...
- keeping equipment clean and maintaining chemical treatment and paint finishes on metal surfaces
- frequent washing minimizes
- the length of time electrolytes are in contact with metals, corrosion
- corrosion removal is performed by personnel who are properly trained in the use of...
- chemical paint remover, abrasive materials, power tools and damage limits
- what type of cleaner should be used when cleaning surfaces in a corrosive environment?
- the mildest possible non corrosive cleaner
- can mask the initial stages of corrosion
- paint coatings
- corrosion products occupy ___ volume than the original metal
- more
- paint surfaces must be inspected often for irregularities such as...
- blisters, flakes, chips, and lumps
- On the galvanic table, metals are arranged in the order of...
- their relative activity in a sea water environment
- galvanic table begins with ___ and proceeds down to ___
- more active (anodic), lest active (cathodic)
- the closer the metals on the galvanic table the more ___ the corrosion
- minimal
- the further the metals on the galvanic table the ___ the corrosion
- greater
- A “galvanic series" applies to a particular...
- electrolyte solution