AME 1101 T3 Corrosion PPT1

types of corrosion and general info as to everything that can cause corrosion in aircraft.

What is Corrosion?

Metal corrosion is the deterioration of the
metal by chemical or electrochemical
attack. This type of damage can take place
internally, as well as on the surface.

How does Corrosion manifest in Copper, Aluminium/Alloy, and Steel?

• On the surface of aluminum alloys and magnesium, it appears as pitting and etching and is often
  combined with a gray or white powdery deposit.

• On copper and copper alloys, the corrosion forms a greenish film; on steel, a reddish corrosion byproduct
  commonly referred to as rust.

Factors Affecting Corrosion.

1. Type of metal

2. Heat treatment and grain direction

3. Presence of a dissimilar, less corrodible metal

4. Anodic and cathodic surface areas (in galvanic corrosion)

5. Temperature

6. Presence of electrolytes (hard water, salt water, battery fluids, etc.)

7. Availability of oxygen

How does electro positivity in metal impact corrosion?

Metals have a wide range of corrosion resistance. The most active metals (those that
lose electrons easily), such as magnesium and aluminum, corrode easily.

The most noble metals (those that do not lose electrons easily), such as gold and silver,
do not corrode easily

Foreign materials in the context of corrosion is what? and how does it impact?

Among the controllable factors that affect the onset
and spread of corrosive attack is foreign material that
adheres to the metal surfaces. Such foreign material
includes; dust,Oil, grease, and engine exhaust residues,Salt water, acid, and welding.

What are the two primary types of corrosion?

direct chemical attack and
electrochemical attack

Direct chemical attack?

An attack resulting from direct exposure of a bare surface to caustic liquid or gaseous agents.(Most common)

Electrochemical Attack?

A type of corrosion where metal atoms lose electrons (oxidize) and turn into metal ions in the presence of an electrolyte, creating a small electrochemical cell on the surface.

Oxidisation is what?

It is one of the more simple versions of corrosion. It is reversed to as dry corrosion or simply oxidisation. It occurs when a metal is exposed to oxygen forming a oxide layer in aluminium this isn't bad as the layer prevents further Oxidisation, however, in iron this Oxidisation will continue and worsen. 

What is uniform corrosion? what does it develop into?

Prolonged exposure to moisture, oxygen, and contaminants (like salt, acids, or pollutants) that form an electrolyte on the metal surface.

This is caused by atmospheric corrosion like exhaust fumes or industrial contaminants. it will initially look like a dulled surface with limited shine and will develop into surface pitting if left unaddressed. 

Pitting corrosion, what it looked like and what it can do?

I will look like white powered deposits and can wear straight through the metal.

Explain how Galvanic corrosion occurs?

When a anode like aluminium is in the close to a cathode like steel in the presence of a electrolyte like salt water. causing corrosion to occurs at a rapid rate.

Concentrated cell corrosion is what? 

Corrosion that occurs when two areas of the same metal have different oxygen or electrolyte concentrations, creating an anode (low O₂) and cathode (high O₂).

In crevices, lap joints, under dirt, paint, or sealant areas where moisture gets trapped and oxygen can’t reach evenly.

The surface contamination here will create a electrolyte that will cause ionic imbalance.

Fretting Corrosion is what and when does it occur? 

Corrosion caused by repeated rubbing or vibration between two metal surfaces under load wearing away protective oxide films and forming oxidised debris. 

Think burnt rivets. you will need to drill out these rivets and move to a larger size. 

Corrosive substances?

Substances that attack aircraft metals by forming electrolytes or chemical reactions — causing or speeding up corrosion.

Like salt water, icing fluid, acid prep solutions, and cleaning agents

Organic growths?

Living organisms like mold, mildew, fungi, and bacteria that can grow on aircraft surfaces, especially where moisture and dirt collect

In places like the fuel tanks, underfloor boards, around lavatories/galleys, and around drain areas. Can lead to corrosion if not addressed.

Brinelling?

Brinelling is surface damage where hard, permanent indentations (pits) form on a metal surface due to excessive static load or impact on ball or roller bearings or races.