Cleaning and Corrosion Control

8083 Chapter 8: Cleaning and Corrosion Control. Module of Materials and Precision.

FAA AC 43-4

Where you would find more in-depth information on the subject of aircraft corrosion.

Direct or electrochemical

Metal corrosion is the deterioration of metal by _ or _ attack.

Aluminum and Magnesium

The two most active metals.

15 days

How often should aircraft in severe climate zones be cleaned, inspected, and lubricated?

Electrochemical

Preventing this is done by eliminating one of the four condition required for this type of corrosion to occur.

Nobility

A measure of how electrically active a metal is.

Anode

On the nobility chart, it is the end most likely to corrode.

Cathode

On the nobility chart, it is the end least likely to corrode.

Intergranular

This type of corrosion may exist without any visible surface evidence.

Intergranular

High Strength aluminum alloys are more susceptible to this type of corrosion if they are not properly heat treated.

Shot peening

A method of increasing the resistance of a metal to stress corrosion cracking by creating compressive stresses on the surface of the metal.

Cyclic fatigue

A metal’s resistane to this may be reduced in a corrosive environment.

Galvanic

This type of corrosion is related to the size of the parts in contact.

Acids alkalies salts

Three most common corrosive agents are _ _ and _ but atmosphere and water may also act as corrosive agents.

Visual inspection

The most widely used technique for the detection and evaluation of corrosion.

Surface

Uniform etch or uniform attack; the most common type of corrosion.

Filiform

Oxygen concentration cell occurring on metal surfaces with an organic coating system.

Filiform

Recognized by worm-like traces of corrosion products beneath the paint film.

Pitting

First noticeable as a white or gray powdery deposit blotching the surface.

Dissimilar metal

Can cause pitting; also known as galvanic.

Metal ion Oxygen Active-passive

Three types of Concentration Cell Corrosion.

Intergranular

An attack along the grain boundaries of an alloy.

Exfoliation

The advanced form of intergranular corrosion.

Eddy current and ultrasonic

Used to detect intergranular corrosion.

Fretting

When two surfaces fit tightly together but can move relative to one another, it causes this type of corrosion.

Fatigue

Involves cyclic stress and a corrosive environment.

Galvanic

Dissimilar metals making electrical contact in the presence of an electrolyte.

Piano hinges

Prime spots for corrosion due to the materials they are made from and the fact they are natural traps for dirt, salts, and moisture.

Helicopter rotor heads and gearboxes

Require frequent corrosion inspections due to their high strength and exposure to the elements.

Chemical or mechanical

Two methods of removing corrosion; depends on the metal and degree of corrosion.

Rust

A metal oxide that does not protect the underlying base metal from further corrosion.

High strength steel parts

You may not use chemical corrosion removers on these without prior approval.

Chemical surface treatment

You may partially restore a damaged anodized aluminum surface with a _ _ _.

Magnesium

You may not use aluminum wool or other metallic cleaning products to clean _ parts.

Negligible patch insertion replacement

Four degrees of corrosion damage: _ damage, needs _, needs _, or needs _.

Anodic

These aluminum coatings provide corrosion resistance and a paint bonding surface.

Cleaning

A regular part of aircraft maintenance.

Aliphatic naphtha

Recommended for wiping down cleaned surfaces before painting.

Aliphatic naphtha

Suitable for cleaning acrylics and rubber.

Bicarbonate soda

Can be used to neutralize acid deposits in lead-acid battery compartments.

Fayed surface

Surface area contact between two overlapping parts.

Anodic

This type of metal will give up electrons most easily.

Electrolyte

A chemical liquid or gas which will conduct electrical current by releasing ions to unite with ions on electrodes

Alodizing

When a non-electrolytic chemical treatment for aluminum alloys is used to increase corrosion resistance and paint-bonding.

Heat treatment

Poor _ _ is a primary cause of intergranular corrosion.

Hydrogen embrittlement

Non-approved cleaning compounds can cause _ _ in metal structures when used to wash aircraft.

Anodizing

The electrolytic treatment for aluminum alloys to increase corrosion resistance

Corrosion

Can be caused by using caustic cleaning products on aluminum structures.

Boric acid

Used to neutralize corrosion of a ni-cad battery.

Ni-cad

This battery type is neutralized by boric acid.

Lead-acid

This type of battery should be neutralized with a solution of sodium bicarbonate.

Pitot tubes and static openings

Should be plugged prior to cleaning to prevent water ingestion.

Dichromate solution

Should be used to clean magnesium engine parts to promote good paint adhesion.

Transparent plastic

First, flush the surface with clean water to prevent scratching when cleaning _ _ surfaces.

Cleaning

First step in treatment and prevention of corrosion on an aluminum alloy.

Mercury

Spilled _ on aluminum causes rapid and severe corrosion that is very difficult to control.

Fine-grit aluminum oxide

May be used to remove corrosion from highly stressed steel surfaces. Also buffing compounds on cloth buffing wheels or nonwoven abrasive pads.

Water break test

To make certain surfaces are clean. Indicates metal surfaces are free of oil, wax, or grease.

Linseed oil

Interior of steel tubing is best protected by a coating of _ _.

Safety

Most important thing in the removal of corrosive products.

Complete

Second most important thing in the removal of corrosive products is that the removal must be _.

Natural state

Corrosion is the tendency for metals to return to their _ _.

Anode cathode electrolyte

What 3 things must be present for corrosion to occur?

Pitting

The most common form of corrosion found on the surface of aluminum and magnesium.

Wash decarbonize scrape

How many magnesium engine parts be cleaned?

Cotton fiber cloths

What can you use with chemical cleaning agents (with flammable agents and atomizing spray equipment)?

Aluminum wool and fiber bristle brushes

What is acceptable to use in cleaning anodized surfaces?