Corrosion in Aircraft

What are the two general forms of corrosion mentioned?

• Stress and fretting corrosion

• Direct chemical and electro-chemical corrosion

• Microbiological and galvanic corrosion

• Pitting and crevice corrosion

Answer explanation

The two general forms of corrosion are direct chemical corrosion, which involves chemical reactions, and electro-chemical corrosion, which involves electrochemical processes. These forms encompass various mechanisms of material degradation.

Which type of corrosion is more likely to occur in aircraft?

• Electro-chemical corrosion

• Crevice corrosion

• Direct chemical corrosion

• Pitting corrosion

Answer explanation

Electro-chemical corrosion is prevalent in aircraft due to the presence of moisture and dissimilar metals, leading to galvanic reactions. This type of corrosion can significantly affect structural integrity, making it a major concern in aviation.

What is a common preventative measure for electro-chemical corrosion?

• Using sacrificial anodes like zinc

• Applying heat treatment

• Increasing the temperature

• Using copper rivets

Answer explanation

Using sacrificial anodes like zinc is a common preventative measure for electro-chemical corrosion. These anodes corrode instead of the protected metal, thus preventing damage.

Which of the following is NOT a condition necessary for corrosion to occur?

• High temperature

• A metallic connector between anode and cathode

• Presence of an anode and a cathode

• An electrolyte such as water

Answer explanation

High temperature is not a necessary condition for corrosion. Corrosion can occur at various temperatures as long as there is an anode, cathode, and electrolyte present, making high temperature irrelevant.

What is the most common type of corrosion affecting airplanes?

• Crevice corrosion

• Microbiological fuel corrosion

• Pitting corrosion

• Stress corrosion cracking

Answer explanation

Crevice corrosion is the most common type affecting airplanes, as it occurs in confined spaces where moisture and contaminants can accumulate, leading to localized corrosion. This makes it a significant concern in aircraft maintenance.

Which material is least likely to corrode among common aircraft materials?

• Steel and iron

• Magnesium alloys

• 2000 series aluminium alloys

• Graphite composites

Answer explanation

Graphite composites are highly resistant to corrosion compared to steel, iron, magnesium alloys, and 2000 series aluminium alloys, making them the least likely to corrode among common aircraft materials.

What is a common cause of stress corrosion cracking?

• High temperature exposure

• Microbiological growth in fuel

• Contact with saline solutions

• High residual stress in parts of a metal object

Answer explanation

High residual stress in metal parts can lead to stress corrosion cracking, as it makes the material more susceptible to environmental factors, causing cracks to form and propagate under stress.

Which of the following is a method to reduce fretting corrosion?

• Increasing the stress on the parts

• Applying a heat treatment

• Using lubricating grease

• Using magnesium alloy bolts

Answer explanation

Using lubricating grease helps reduce fretting corrosion by creating a barrier between the surfaces, minimizing direct contact and wear. This method is effective in preventing the micro-movements that lead to corrosion.

What is a suitable metal for rivets to prevent rapid corrosion?

• Magnesium

• Zinc

• Stainless steel

• Copper

Answer explanation

Stainless steel is a suitable metal for rivets as it contains chromium, which forms a protective layer that prevents rapid corrosion. In contrast, magnesium and zinc are more prone to corrosion, while copper can also corrode in certain environments.

Which of the following is a factor that can cause corrosion in aircraft?

• Using only similar metals

• Incorrect heat treatment

• Absence of electrolytes

• Low humidity environments

Answer explanation

Incorrect heat treatment can lead to structural weaknesses in aircraft materials, making them more susceptible to corrosion. Other options do not directly contribute to corrosion in the same way.