Corrosion

Zinc

Galvanizing protects steel by covering it with a layer of ____.

Direct Chemical Attack

If the entire surface is covered with a strong electrolyte, corrosion can develop uniformly over an extensive area.

Anode

In an electrochemical reaction, it is the _______(anode or cathode) which will be eaten away.

Baking Soda

Battery acid from a lead-acid battery is neutralized with a solution of ____ ____ .and water

Boric Acid

Battery acid from nickel-cadmium batteries is neutralized with a solution of ____ ____ .and water

Water Break Test

Before applying an alodizing agent (Alodine 1201) a ____ ____ test must be performed.

Zinc Chromate, Vinyl

Before joining dissimilar metals they are prepared by spraying two coats of ___ _____ primer and placing a strip of ____ tape between the surfaces before they are assembled.

Steel

Corrosion must never be removed from aluminum with ___ brushes or with ___ wool.

Concentration Cell Corrosion

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.

Wash Primer (Corrosion)

Filiform corrosion forms mostly under a(n) _____ ______ finish.

Exfoliation Corrosion

An extreme case of intergranular corrosion. Occurs in channels or angles where grain structure is more layer-like. Causes material to separate or delaminate.

Classifications of Corrosion

1) Chemical 2) Electrochemical

Four Requirements for Formation of Corrosion

1) Presence of a metal that will corrode (anode). 2) Presence of a dissimilar conductive material (cathode) which has less tendency to corrode. 3) Presence of a conductive liquid (electrolyte) 4) Electrical contact between anode and cathode (usually metal-to-metal contact, or a fastener).

Corrosion Treatment Steps

1) Remove as much corrosion as possible. 2) Neutralize residual material. 3) Restore the protective surface film.

Common Agents Causing Chemical Corrosion

1) Spilled battery acid or fumes. 2) Residual flux deposits - from inadequately cleaned, welded, brazed, or soldered joints. 3) Entrapped caustic cleaning solutions.

Primers

1) Zinc Chromate 2) Wash 3) Epoxy

Wash Primer

A self-etching primer used on aluminum or magnesium. It is often used to prepare the surface for zinc chromate primer.

Epoxy Primer

A two-part catalyzed paint material used to provide a good bond between surface and top-coat. (Popular for use under polyurethane finishes)

Intergranular Corrosion

A type of corrosion which is an attack along the grain boundaries of a material. The grain boundary and grain center can react with each other as anode and cathode when in contact with an electrolyte.

Chromic Acid

After the corrosion has been mechanically removed from an aluminum alloy, the surface should be neutralized by treating it with a 5% solution of _____ ____.

Cladding

Aluminum allows can be protected from corrosion and at the same time made attractive in appearance by coating them with a layer of pure aluminum, this is known as _____.

Aluminum Oxide

Aluminum alloy are protected from oxidation by the formation of a(n) ________ _____ film on its surface.

Zinc Chromate

An alkyd resin, corrosion-inhibiting primer that can be used on almost all metal surfaces. Moisture releases chromate ions to inhibit the formation of corrosion, and the alkyd resin forms a good bond for a/c finishes.

Chromic Acid Etch

An aluminum surface is typically roughened with a mild ____ ____ ____, or by the formation of an oxide film through anodizing or alodizing.

Drain Holes

Bilge areas are ideal for the formation of corrosion because of the constant exposure to an electrolyte. They are also prone to accumulate water so are provided with ____ ___.

Special Exterior Cleaning

Brush or spray the cleaning mixture onto the surface and allow it to stand for a few minutes, scrub heavily soiled areas with a soft bristle brush to completely loosen the dirt, than rinse off with high-pressure stream of warm water.

General Exterior Cleaning

Brush or spray the cleaning mixture onto the surface and allow it to stand for a few minutes, than rinse off with high-pressure stream of warm water.

Abrasive Blasting

Corrosion removal on ferrous metals can be accomplished by using abrasive paper or wire brushes, but the most effect way is by ______ ______, accomplished by the use of sand, aluminum oxide, or glass beads.

Is

Dye penetrant inspection ___ (is or is not) an effective inspection method to detect stress corrosion cracks.

Is Not

Dye penetrant inspection ___ (is or is not) effective when used on porous materials.

Sacrificial

Cadmium plating protects steel parts from corrosion by the process of _____ corrosion.

Pure Aluminum

Clad aluminum is protected by a layer of ____ _______ on the aluminum alloy core.

Electrochemical

Corrosion is a(n) ___________ action in which a metal is changed into a chemical salt.

Water-Displacing, Waxy Grease

In order to protect cables from corrosion you should spray them with _____ ________ type of lubricant. For those in a seaplane you should coat them with a _____ ______ such as Par-Al-Ketone.

Quench

Intergranular corrosionof aluminum alloys is usually caused by delaying the ______ during heat treatment.

Amalgamation

Mercury attacks aluminum by a chemical reaction known as _______. In this process, the mercury attacks along the grain boundaries within the alloy, and in a very short time completely destroys it.

Does

Magnesium ___ (does or does not) naturally form a protective oxide coating on its surface.

Aluminum Wool, Aluminum Wire Brushes

Medium-severe corrosion on aluminum alloys can be removed with _____ ____ or _____ ____ ____

Oxidation or "Dry Corrosion"

When a metal such as aluminum is exposed to a gas containing oxygen, a chemical reaction takes place on the surface between the metal and the gas.

Sacrificial 2

Metal spraying protects steel parts from corrosion by the process of _____ corrosion.

Electrochemical Series

Metals are arranged to show the relative ease with which they ionize in what is called the _______ _____.

Water

Microbial growth in fuel tanks of a turbine powered a/c may cause corrosion by holding ____ against the aluminum alloy structure

Air, Moisture

Nickel and chrome-plating protect a steel part from corrosion by preventing ___ and _____ from reaching the surface of the metal.

Scotch-Brite Pads

Nylon scrubbers such as ____-_____ ____ can be used to remove mild corrosion on aluminum alloys.

Stress Corrosion

Occurs when metal is subjected to a tensile stress in the presence of a corrosive environment.

Alodizing

When small parts are fabricated in the field or when the protective anodizing film has been damaged or removed, the part can have a protective film applied through chemical rather than electrolytic process, this is known as ______.

Gently, No Abrasive or Stiff Brushes

Rubber deice boots should be cleaned this way.

Rotary Files, Power Grinders

Severely corroded aluminum alloys require drastic treatment to remove all corrosion, use of _____ ____ or _____ ______ using rubber wheels impregnated with aluminum oxide are used to grind out corrosion damage.

Soap & Water

Since most cleaning solvents are petroleum based, these are the only approved solutions for cleaning tires.

Fretting Corrosion(False Brinelling)

When two surfaces fit tightly together but can move relative to one another, this type of corrosion occurs. Appears as black and gooey. Occurs around rivets in a skin(Smoking rivet).

1:5 or 1:3

When washing the exterior of an aircraft use this ratio mixture of water and emulsion-type cleaner.

Filiform Corrosion

Special form of oxygen concentration cell corrosion or crevice corrosion which occurs on metal surfaces having an organic coating system. Recognized by its fine threadlike line under a polyurethane enamel finish. Results when the wash primer use on a metal has not been properly cured.

Non-Metallic

Stiff ____ _____ bristle brushes may be used to remove corrosion from the surface of magnesium.

1:2(Exhaust)

Stubborn exhaust stains may require a __ mixture of varsol or kerosene.

Part is Retreated

The appearance of a powder on the surface of a piece of aluminum alloy that has been treated with Alodine is an indication of improper application. How is this condition corrected?

1:2

The engine cowling and wheel well area usually have grease or oil deposits that require special treatment, use this ratio mixture of water and emulsion cleaner.

Anodizing

The process of applying an oxide film is performed in the factories by an electrolytic process known as ______.

Alclad

The protection afforded by an aluminum oxide coating is the principle reason for ____.

Microbes

These organic bodies live inside the water in the bottom of a jet fuel tank. If left untreated they will corrode through the tank and cause a leak.

Scratched

This can occur on plastic or plexiglass surface finish if rubbed with a dry cloth.

Galvanic Corrosion

This common type of corrosion occurs any time two dissimilar metals make electrical contact in the presence of an electrolyte.

Aliphatic Naptha

This is a hydro-carbon solvent that dissolves oil and grease but does not harm rubber or acrylic components. (Use natural cloth, cotton)

Chemical Corrosion

This results from direct exposure of a bare surface to caustic liquid or gaseous agents.

Hydrogen Embrittlement

This results when a chemical reaction produces hydrogen gas that is absorbed into a metal. This reduces a metal's ductility and allows the formation of cracks and stress corrosion.

Aromatic Naptha

This type of Naptha is damaging to rubber and acrylic compounds.

Pitting Corrosion

This type of corrosion is likely a result of uniform surface corrosion left untreated. Usually detected by the appearance of clumps of white powder on the surface.

High Viscosity Water-Rinsable

This type of paint remover is usually best for use on a/c surfaces.

Uniform Surface Corrosion

Where an area of unprotected metal is exposed to an atmosphere containing battery fumes, exhaust gases, or industrial contaminants, a uniform attack over the entire surface occurs.

Alkalis

While both materials will corrode metal, aluminum alloys are more vulnerable to ______ (acids or alkalis).

May Cause Minute Scratches

Why should wire brushes not be used to remove corrosion from highly stressed steel parts?

Linseed Oil

To protect welded steel tube mounts from internal corrosion the tubing should be periodically filled with hot _____ ___ or other type of tubing oil.

Dry-Cleaning Solvent or Naptha

To remove oil, grease or soft preservative compounds, you should use this.

Bon Ami,

Very mild corrosion on aluminum alloys may be removed by using a neutral household cleaner such as __ __ (do not get in contact with chlorine).

Linseed

Welded steel tube engine mounts are protected from internal corrosion by coating the inside of the tubing with hot ___ oil.

Hot Water

Welding flux on aluminum alloy may be removed by washing it with ___ ____.

Wash With Fresh Water

What should be done to a seaplane when it is beached after it has been operated in salt water?

Glass Beads

____ ____ smaller than 500 mesh can be used to remove corrosion from pits on aluminum alloys. (Examine with 5-10 power magnifying glass to ensure all corrosion has been removed)

Magnesium

_____ is particularly vulnerable to corrosive attack from salt solutions.