Term
| This type of corrosion can occur under scale and surface deposits and under loose-fitting washers and gaskets that do not prevent the entry of liquid between them and the metal surface. |
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Definition
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Term
| This type of corrosion can proceed inward from a surface exposed to air or may exist in an immersed structure. |
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Definition
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Term
| A special form of crevice corrosion, which usually takes the form of pitting when abhsorptive debris such as paper, wood, cloth are in contact with a metal surface that becomes wetted periodically. |
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Definition
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Term
| A special form of oxygen-cell corrosion occuring beneath organic or metallic coatins on steel, zinc, aluminum, or magnesium. |
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Definition
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Term
| This type of attack results in a fine network of random "threads" of corrosion product developed beneath the coating material with a shallow grooving of the metal surface. |
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Definition
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Term
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Definition
*number of electrons lost in an electrochemical reaction
*are related to the moles of metal
*consumed at the anode and deposited at the cathode. |
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Term
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Definition
*calculates the electrode voltage
* based on the free energy of the electrode and
*the effects of the reactants and temperature. |
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Term
| Corrosion Potential is also called? |
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Definition
rest potential
open-circuit potential
freely corroding potential
native potential |
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Term
| An electrode whose open-circuit potential is constant under similar conditions of measurement, which is used for measuring the relative potentials of other electrodes |
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Definition
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Term
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Definition
| *change from the open-circuit potential *caused by current flow |
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Term
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Definition
8reduction of chemical reactivity of a metal
*or alloy under certain circumstances. |
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Term
curves for specific
alloys enable the user to use
anodic protection to control
corrosion. |
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Definition
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Term
| are used to predict the stability of metals and corrosion products in environments of varying pH. |
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Definition
| Pourbaix Diagrams (potential vs ph) |
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Term
| is a cathodic depolarizer which shifts potentials in the cathodic direction. |
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Definition
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Term
| ___ - ____ oxygen concentration will cause corrosion in the low oxygen areas. |
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Definition
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Term
| A low concentration of metal ions at one point on a metal surface and higher concentration at another point will produce a difference in ___ between the two points. (Nernst equation) |
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Definition
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Term
|
Definition
*technique
*reduce the corrosion of a metal surface
*by making that surface the cathode of an electrochemical cell |
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Term
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Definition
| Polarization to a more oxidizing (anodic) potential to achieve a reduced corrosion rate by the promotion of passivity. |
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Term
| Corrosion Rate Measurement |
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Definition
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Term
| What does a corrosion cell have to have in order for corrosion to take place |
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Definition
*anode
*cathode
*metallic pathway
*electrolyte |
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Term
| where does polarization happen |
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Definition
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Term
| If polarization increases, then the current ___? |
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Definition
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Term
| If the current goes up, then the corrosion rate goes? |
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Definition
|
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Term
| 3 different types of polarization |
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Definition
*activation
*concentration
*ohmic (IR) |
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Term
|
Definition
| factors that slow reactors down |
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Term
| Where does passivity happen? |
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Definition
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Term
| If you increase the temperature by 10 degrees Celsius, what happens to the corrosion rate? |
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Definition
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Term
| What is a big indicator of your corrosion rate? |
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Definition
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Term
| What is the favorable condition for corrosion (anode,cathode)? |
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Definition
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Term
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Definition
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Term
| Corrosion that occurs at localized sites on a metal surface, while the surrounding area is corroding at a much slower rate. |
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Definition
| localized corrosion (local cell) |
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Term
| (local cell) Differences among small nearby areas on the metal surface caused by |
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Definition
*metal differences
*environment differences
*impressed currents |
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Term
| (Pitting) May be holes filled with corrosion products with ___ or ___. |
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Definition
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Term
| Remedies for pitting corrosion |
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Definition
*Cathodic Protection
*Inhibitors
*Plating with another alloy
*Protective coating
*Agitation of the environment |
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Term
| Pitting corrosion difficulties |
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Definition
*Difficult to find and determine the most severe areas
*Difficult to monitor
*Difficult to design against |
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Term
| Also called Differential Aeration |
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Definition
| Oxygen Concentration Cell |
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Term
| A corrosion cell resulting from a potential difference caused by different amounts of oxygen dissolved at different locations |
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Definition
| oxygen concentration cell |
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Term
| Oxygen concentration cell remedies |
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Definition
*Exclude oxygen (de-aeration)
*Keep surfaces clean and avoid crevices
*Change velocity
*Material selection |
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Term
| A galvanic cell caused by a difference in metal ion concentration at different locations on the same metal surface. |
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Definition
| Metal Ion Concentration Cell |
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Term
| Metal Ion Concentration Cell remedies |
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Definition
*Maintain uniform electrolyte velocity
*Avoid crevices
*Overcome with CP |
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Term
| crevice corrosion remedies |
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Definition
*Use butt joints instead of lap joints
*Fill crevices with a joint compound
*Eliminate crevices in the design
*Provide complete drainage
*Avoid contact or absorptive materials with metal
*Coat the metal surface |
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Term
| Localized corrosion resulting from the formation of a concentration cell in a crevice between two metal surfaces or between a metal and nonmetal. |
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Definition
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Term
| Differential aeration develops during the drying period which leads to pitting. |
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Definition
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Term
| Poultice Corrosion remedies |
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Definition
*Avoid contact of absorptive materials with a metal surface
*Paint surfaces contacting such materials
*Design to prevent moisture in such materials |
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Term
| Deformation caused by corrosion in lap joints of commercial airlines, which is accompanied by a bulging or pillowing between rivets resulting from the increased volume of the corrosion product over the original material. |
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Definition
|
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Term
|
Definition
| Targeted inspection with various inexpensive, rapid, and nondestructive optical-imaging techniques. |
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Term
| Also known as Underfilm Corrosion |
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Definition
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Term
| Filiform corrosion remedies |
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Definition
*Careful surface preparation prior to coating
*Use of coatings that are resistant to filiform corrosion
*Careful inspection of coatings to insure holidays are minimized |
|
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Term
| Also known as Dissimilar Metal Corrosion |
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Definition
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Term
| Accelerated corrosion of a metal because of an electrical contact with a more noble metal or nonmetallic conductor in a corrosive electrolyte |
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Definition
|
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Term
| galvanic corrosion remedies |
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Definition
*Electrically isolate the two metals
*Select metals in close proximity on the galvanic series
*Avoid unfavorable area ratio
*Design for replacement of the anodic area
*Coat the cathode |
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Term
| A subtle form of galvanic cell that can produce pitting in a liquid environment when a more cathodic metal is plated out of solution onto a metal surface. |
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Definition
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Term
| Deposition corrosion remedies |
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Definition
*Remove the ions
*Change materials (glass-reinforced plastic)
*Utilize chemical inhibitor |
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Term
| Selective removal by corrosion of one of the elements of an alloy by either preferential attack or by complete dissolution of the matrix. |
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Definition
| Dealloying (Selective Attack) |
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Term
| What is the name of the dealloying corrosion in which the metallic constituents (iron) are removed from cast iron? |
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Definition
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Term
| Localized erosion corrosion caused by turbulence or impinging flow. |
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Definition
|
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Term
|
Definition
*Material selection
*Reduce velocity
*Design |
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Term
| Damage caused by the formation of voids in a liquid due to turbulence or temperature causing local zones to fall below vapor pressure. |
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Definition
|
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Term
|
Definition
*Raise the vapor pressure
*Inhibitors
*Use less ductile more brittle metal
*Cathodic Protection
*Use of softer metal in the case of rubber |
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Term
| Deterioration at the interface of two contacting surfaces under load which is accelerated by their relative motion. |
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Definition
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Term
| Fretting corrosion remedies |
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Definition
*Use mating surfaces of differing hardness
*Eliminate movement by increasing the load or roughing the surfaces
*Exclude air by using cements or sealants
*Lubrication |
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Term
| Microstructure corrosion which occurs along the grain boundaries. |
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Definition
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Term
| Intergranular corrosion prevention methods? |
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Definition
*Material Selection avoiding susceptible materials such as aluminum, copper alloys, and 18-8 stainless steel
*Careful heat treatment of susceptible alloys (follow welding procedures meticulously) |
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Term
| In these types of intergranular corrosion, there are no stresses involved |
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Definition
*Exfoliation
*Sensitization
*Weld Decay |
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Term
| intergranular corrosion common to aluminum caused by improper quenching. |
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Definition
|
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Term
| extreme case of lamellar exfoliation may also be caused by extensive cold work. |
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Definition
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Term
| Austenitic SS may be sensitized to intergranular attack when heated to a range of 400 to 900 degrees Celsius then short times to 750 degrees C. |
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Definition
| Sensitization of Stainless Steel |
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Term
| This causes a chromium depleted zone which has a difference in potential from the chromium rich zones. |
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Definition
| Sensitization of Stainless Steel |
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Term
| Weld decay on SS is another example of this intergranular attack. |
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Definition
| Sensitization of Stainless Steel |
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Term
| Corrosion occurs randomly across the grain structure disregarding the grain boundaries. |
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Definition
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|
Term
| Corrosion occurs randomly across the grain structure disregarding the grain boundaries. |
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Definition
|
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Term
| Transgranular corrosion prevention methods |
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Definition
*Material Selection
*Reduce the tensile stresses
*Cathodic Protection |
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Term
| examples of transgranular corrosion |
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Definition
*Stress Corrosion Cracking
*Corrosion Fatigue |
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Term
| General term that describes the brittle fracture of a normally ductile material in which the corrosive effect of the environment is a causative factor. |
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Definition
|
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Term
|
Definition
|
|
Term
| Hydrogen Embrittlement (HE) - |
|
Definition
|
|
Term
| Hydrogen Induced Cracking (HIC) - |
|
Definition
|
|
Term
| Hydrogen Stress Cracking - |
|
Definition
|
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Term
|
Definition
|
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Term
|
Definition
|
|
Term
| Early failure of a metal by cracking when it is subjected to cyclic stresses. |
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Definition
|
|
Term
| Corrosion fatigue remedies |
|
Definition
*Shot Peening
*Coatings
*Inhibitors
*Cathodic Protection |
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Term
| Stepwise internal cracks that connect adjacent hydrogen blisters on different planes in the metal or to the metal surface. |
|
Definition
| Hydrogen Induced Cracking (HIC) |
|
|
Term
| A loss of ductility of a metal resulting from absorption of hydrogen |
|
Definition
| Hydrogen Embrittlement (HE) |
|
|
Term
| The formation of hydrogen blisters resulting from excessive internal hydrogen pressure which appear as blisters near the surface of low strength metals |
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Definition
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|
Term
| Cathodic protection may ___ these cathodic forms of corrosion by driving more hydrogen into the metal. |
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Definition
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|
Term
| Cracking of a metal caused by contact with a liquid metal. |
|
Definition
| Liquid Metal Cracking (LMC) |
|
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Term
| Mercury causes cracking of copper or Monel. |
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Definition
|
|
Term
| Zinc in the liquid state causes cracking of stainless steel or high-nickel alloys. |
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Definition
|
|
Term
| Steel can be cracked by liquid tin, cadmium, zinc, lead, bismuth, copper, and antimony. |
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Definition
|
|
Term
| Cadmium can attack titanium. |
|
Definition
|
|
Term
| Cracking of a material produced by the combined action of corrosion and tensile stress (residual or applied). |
|
Definition
| Stress Corrosion Cracking (SCC) |
|
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Term
|
Definition
*Material change
*Environmental change
*Barrier coatings
*Electrochemical techniques
*Design |
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