Corrosion Flashcards
Metal corrosion
the deterioration of the metal by chemical or electrochemical attack.
three conditions necessary for corrosion to occur?
the presence of an electrolyte, an anode and a cathode and a conductor.
Electro-chemical attack?
the process of one metal giving up electrons (anode) to another metal (cathode). To replace the electrons the anode loses, it gains them from the electrolyte. The anode corrodes the cathode does not.
direct chemical attack?
occurs when a caustic agent comes in direct contact with the bare surface metal and produces corrosive by products.
What is an Electro-chemical attack comparable with? Why?
An electro-chemical attack is comparable with a dry cell battery because both have an electrolytic reaction.
What is an anode?
.
the positive plate that gives up electrons to the cathode and corrodes.
What is a cathode?
the negative plate that gains electrons from the anode
What can a mechanic do to prevent corrosion from ever occurring?
by using a protective coating, adequate cleaning, keeping drain holes free of obstructions, and sealing the aircraft against water during foul.
Uniform Surface corrosion
An even dulling of the surface caused by exposure to corrosive agents.
Pitting corrosion
Next step after uniform surface. Pits or clumps of white powder appear on anodic area
Inter-granular corrosion
Internal corrosion along grain boundaries
Exfoliation corrosion
An extreme case of intergranular corrosion that causes metal layers to delaminate
Galvanic corrosion
Occurs When two dissimilar metals with different potentials come into direct contact and set off an electron flow.
Concentration Cell corrosion
Occurs when two metals are joined together and moisture settles in creating a corrosion cell.
Stress corrosion
Occurs When a metal is subjected to a tensile stress in a corrosive environment.
