Cleaning And Corrosion Flashcards
When does corrosion happen
Corrosion happens when metals are exposed to water and air
Why is aircraft cleaning important ?
Making sure the aircraft is clean is important because DIRT can cover up damaged components as well as trap moisture and solvents that lead to corrrosion
What is hydrogen embrittlement?
When you use the nonapproved chemicals and cleaning compound, hydrogen embrittlement can occur , a chemical reaction occurs and hydrogen gas is absorbed into the metal, this reduces a metals ductility and allows the formation of cracks and stress correction
What is used to remove oil , grease, or soft preservative compounds ?
Naphtha is used to remove oil , grease , and soft preservatives
What are the two most common types of naphtha ?
The two most common are aliphatic and aromatic
What is aliphatic naphtha ?
It’s a hydrocarbon solvent that dissolves grease and oil but does not harm rubber or acrylic components
What is aromatic naphtha ?
Aromatic attacks rubber and acrylic, frequently used to wipe down cleaned surfaces before painting
What are corrosive agents
Corrosive agents are substances that cause corrosion. Example water , salt and oxygen
Types of corrosion looks explain
Aluminum and magnesium corrosion is grey or white powdery deposit
Copper and copper alloy is green
Steel is reddish brown
Anodic reaction
Where the metal loses electrons and corrodes
Cathodic reaction
Where electrons are gained
Electrochemical series
A chart showing which metals give up electrons easier ( corrodes easier )
Explain oxidation
Oxidation is known as dry corrosion and it happens when a metal is exposed to a gas containing oxygen
Explain uniform surface corrosion
An unprotected metal is exposed to an atmosphere containing battery fumes , exhaust gases , or industrial contaminants
Explain pitting corrosion
Pitting is a result of uniform surface corrosion left untreated, it looks like powdery salt on the surface
Explain galvanic corrosion
When two not the same metals come in contact in the presence of an electrolyte. For example aluminum plates with steel screws.
Explain concentration cell corrosion
The deterioration of parts of a metal surface at different rates
When does oxygen concentration cell corrosion occur
When water covers the surface of an aluminum aircraft skin and seeps into the cracks
Metallic ion concentration forms
In the closed areas between the faying surfaces
Active passive cells happen on
Metals that use a passive film for corrosion protection
Explain filiform corrosion
Occurs on an organic coating system , usually occurs when the wash primer has not been properly cured
Intergranular corrosion
An attack along the grain boundaries
Exfoliation corrosion
An extreme case of intergranular corrosion
Stress corrosion
Occurs when metal is subjected to a tensile stress in the presence of a corrosive environment
Fretting corrosion
Occurs around rivets in a skin and is indicated by dark deposits around the rivet heads. (Rivet smoking )
Types of corrosive agents
Salts, water , mercury , air
What are the two types of ultrasonic indications or corrosion detection ?
The pulse echo and the resonance method
What are some corrosion prone areas
Engine exhaust , battery compartments , food service areas , landing gear , fuel tanks , control cables
Process of corrosion treatment
Remove as much corrosion as possible , neutralize any residual material, and restore the protective surface film
What can be used as a protective coating for aluminum
Paint , cladding , and surface oxide film
What do Primers like epoxy do
Used under paint to inhibit the formation of corrosion on aluminum aircraft
How to remove corrosion from ferrous metals
Abrasive blasting
Ferrous metals can be pretreated to protect them from corrosion
Using methods like nickel , chrome plating, cadmium plating , applying primers like zinc chromate
