FAA Aviation Mechanic Airframe (AMA)Airframe StructuresHard
A technician finds surface corrosion on a magnesium alloy landing gear housing. Which corrosion treatment is specifically appropriate for magnesium alloys, as opposed to the chromate conversion coatings typically used on aluminum?
- AA dichromate chemical treatment process specifically formulated for magnesium alloys
- BAlodine chromate conversion coating identical to that used on aluminum
- CSulfuric acid anodizing identical to the aluminum anodizing process
- DDirect cadmium electroplating without any prior surface treatment
Show answer & explanationAnswer & explanation
Correct answer: A. A dichromate chemical treatment process specifically formulated for magnesium alloys
Magnesium alloys require their own specific corrosion protection treatments, such as a dichromate chemical treatment process, because they are highly anodic and corrode much more aggressively than aluminum. Standard aluminum treatments like Alodine or sulfuric acid anodizing are not formulated for magnesium and would not provide adequate protection.
Why the other options are wrong
- B. Alodine is formulated for aluminum oxide chemistry and is not suitable for magnesium surfaces.
- C. Aluminum sulfuric acid anodizing baths are not compatible with magnesium alloy surfaces.
- D. Cadmium plating requires proper surface preparation and is not typically applied directly to magnesium without pretreatment.
Magnesium Alloy Corrosion Treatment
A dichromate-based chemical conversion treatment specifically formulated to protect magnesium alloy surfaces from corrosion, distinct from aluminum treatments.
- Magnesium is highly anodic and corrodes more readily than aluminum
- Requires dedicated treatments (e.g., dichromate process) rather than aluminum's Alodine/anodizing
- Magnesium components are common in older aircraft wheels, gearboxes, and control surfaces
Memory trick: Magnesium needs its own dichromate 'medicine,' not aluminum's Alodine