Aircraft Corrosion Control Vocabulary

Rivet smoking

Fretting corrosion that occurs around rivet heads & that leaves a black residue trail behind the rivet typically found on the fuselage skin.

Oxygen Concentration cell corrosion

(A lack of oxygen) when water covers the surface of an aluminum aircraft skin and seeps into the cracks between lap joints. can occur on Aluminum, magnesium or on ferrous metals. It forms under marking tape of ferrules on aluminum. it forms in the areas where there is a deficiency of oxygen.

Fretting Corrosion

(also called false brinnelling) 2 surfaces tightly fit together but move relative to one another. Is the result of the abrasive wear caused by two surfaces rubbing against each other, this rubbing known as fretting prevents the formation of a protective oxide film exposing the metal to the atmosphere. Example, occurs around rivets in a skin and is indicated by dark deposits around the rivet heads.

False brinnelling

Another name for Fretting corrosion, the term is used because instances of this corrosion resemble Brinnel Markings or pressure indentations.

Oxygen concentration cells, metal ion concentration cells, and active passive cells.

Are the three general types of concentration cell corrosion

Sacrificial Corrosion

A method of corrosion protection in which a surface is plated with a metal less noble than itself. Any corrosion will attack the plating rather than the base metal.

Exfoliation Corrosion

Occurs along the grain boundaries and causes the material to separate, or delaminate. It occurs in extruded materials, such as channels or angles, is an extreme case of intergranular corrosion.

Galvanic Corrosion

Occurs anytime two dissimilar metals make electrical contact in the presence of an electrolyte, it provides a path for electrons. For example, galvanic corrosion can take place where dissimilar metal skins are riveted together, or where aluminum inspection plates are attached to the structure with steel screws.

Stress Corrosion

Occurs when metal is subjected to tensile stress in the presence of a corrosive environment. the stresses can form due to improper quenching after heat treatment or from an interference fit of a fastener. common locations are, between rivets in a stressed skin, around pressed-in bushings, and tapered pipe fittings.

Oxidation or Dry Corrosion

One of the simpler forms of corrosion, forms when a metal comes in contact with corrosion. It also forms when a metal such as AL is exposed to a gas containing oxygen, a chemical reaction takes place on the surface between the metal and the gas.

Surface corrosion

Oxidation across the surface of a metal is caused by the reaction of metallic surfaces with atmospheric contaminants, such as chlorine or sulfur compounds, oxygen or moisture.

Intergranular Corrosion

The formation of corrosion along the grain boundaries within a metal alloy and can not been seen.

Pitting Corrosion

Uniform surface corrosion that's been left untreated . Pits forms as localized anodic areas and corrosive action continues until an appreciable percentage of the metal thickness is converted into salts. Pitting is usually detected by the appearance of clumps of white powder on the surface of the metal as it is corroded.

Filiform corrosion

is a special form of oxygen concentration cell corrosion or crevice corrosion which occurs on metal surfaces having an organic coating system, often caused when wash primer used has not been properly cured. recognized by its fine threadlike lines under a polyurethane enamel finish. It shows itselft as a puffiness under the paint and is first noticed around rivet heads and along the lap joints of skins. (puffiness underneath the paint caused by powdery salts).

Concentration cell corrosion

or crevice corrosion, is corrosion of metals in a metal-to-metal joint, corrosion at the edge of a joint even though the metals are identical, or corrosion of a spot on a metal's surface covered by a foreign material.