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| What problems are associated with ni-cad batteries? |
Electrolyte from ni-cads is potassium Hydroxide, alkaline. Neutralize with boric acid or vinegar, mild acidic solution. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What problems are associated with lead-acid batteries? |
Vapor and dripping. The electrolyte escapes and causes corrosion. Need to have a non-corrosive battery box, or paint with Bituminus paint. Vapors need to be vented overboard via a container to neutralize acid. Neutralize acid with bicarbonte of soda. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What corrosion issues are related to Jet A fuel. |
Water entrapment and biological organisms that live and die in water. Once dead that sink and cause a film on the bottom of the fuel tank and could trap water. need to add a Biocide, PRIST. Contaminated tanks appear green or black. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is Filliform Corrosion? |
Oxidation under a painted area which causes "Worm-like" threads of corrosion. Typically caused by edges not being painted. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is Sacrificial Corrosion. |
A more anodic metal is added as protection and is sacrificed (replaced) to protect aircraft. Typically zinc. Cadmium on screws is also somewhat sacrificial. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is a smoking rivet? |
Fretting Corrosion between rivet and skin. Causes wind streaking from rivet head. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is Fretting Corrosion? |
Two highly stressed metals that move against one another. Creates new metal area open to O2 and corrosion. Think smoking rivet. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is stress corrosion? |
Chemical corrosion that occurs under cycliced tensile stress. Cycle wear and chemical corrosion. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is fretting? |
Two metals that are not suppose to move against one another do. More abrasive process of metals exposes more metal thus more corrosion, causing fretting corrosion. |
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CAVUMark Sun, 18 May 2008 23:08:09 GMT |
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| What is faying action? |
Slight abrasive activity between two metals, creates metal ions and sets up metals for corrosive process. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| Describe Metal Ion Concentration corrosion. |
Galvanic process where faying process creates metal ions under lap joint (EX) and stagnants and becomes cathodic. Area just outside joint becomes anodic and corrodes. |
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CAVUMark Sun, 18 May 2008 23:09:56 GMT |
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| Describe O2 concentration corrosion. |
Galvanic process between two metals (lap joint, under tape, screws) where the O2 concentration is different between the two areas, (between metals and just outside). Area under joint has less O2 becomes stagnant and anodic. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What are the two Concentration Cell corrosion types? |
1) O2 concentration
2) Metal Ion Concentration |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| Can more than one type of Corrosion take place simultaneously? |
Yes, could have galvanic to intergranular to exfoliation. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is Exfoliation Corrosion? |
Extreme form of Intergranular Corrosion where metal separates along grain structure and "grows". Layers start to separate causing delamination. Poor manufacturing process. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What causes Intergranular Corrosion? |
Improper heat treating and/or welding setting up large grain in worked metal. Different alloys in metal electro-mechanically corrode. |
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CAVUMark Sun, 18 May 2008 23:11:41 GMT |
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| How is Intergranular Corrosion spotted? |
May not be visible possible some blister on metal surface. Will probably need to replace part. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is Intergranular Corrosion? |
Corrosion inside metal between 2 alloys caused by improper heat treating. Seen a lot in copper alloyed AL. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is Aluminum Oxide? |
Surface corrosion that protects the metal underneath, creates corrosion resistance. Process is called Passivity. Surface corrosion left unchecked will cause Pitting Corrosion. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What is rust on steel? |
Iron Oxide FE2O3, opening in the surface of the metal allows oxygen to penetrate and creates rust, rust opens exposes more metal until nothing but rust. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What 2 forms of electro-mechanical corrosion can take place |
1) single metal, within metal alloys itself,
2) two metals, between different metals. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| What three items are needed for Electro-mechanical corrosion. |
1) electrical potential between metals
2) electrical path between anode and cathode
3) electrolyte, water, moisture, salt for return path of electrons |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| Describe Oxidation |
Dry corrosion, metal reacts with oxygen on the surface of the metal.
Steel = rust
Al = AL oxide, unbroken surface for protection. Process is Passivity. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| Describe Electro-mechanical |
Electrolysis or galvanic action between two dissimilar metals. Anode and cathode where anode corrodes. |
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CAVUMark Sun, 18 May 2008 15:26:00 GMT |
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| Describe direct Chemical corrosion. |
Metal reacts with oxygen and metal is changed to a chemical salt. Trys to return to its natural state.
AL with moisture containing Hydrocholric acid = AL cholride (salt)
AL with Oxygen form Al Oxide (thin covering protecting AL) |
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CAVUMark Tue, 20 May 2008 21:30:31 GMT |
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| What are the type of aircraft corrosion? |
Direct Chemical
Electro-mechanical
Oxidation |
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CAVUMark Sun, 18 May 2008 15:25:59 GMT |
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