After cleaning the crankcase and accessory gearbox, which corrosion protection method is used?

After cleaning the crankcase and accessory gearbox, which corrosion protection method is used?

• A. Zinc phosphate
• B. Paint
• C. Alodine
• D. Chromate

Answer: (C)

Alodine, a chromate conversion coating, is used after cleaning aluminum crankcase and accessory gearbox parts. This coating chemically bonds to aluminum to form a thin, durable protective film that blocks moisture and salts and provides an excellent surface for primer and paint adhesion. It’s the preferred corrosion protection step for aluminum alloys in overhaul work because it both guards against corrosion and improves paint adhesion, which isn’t as effectively achieved by applying paint alone or by other coatings intended for different metals. Zinc phosphate is typically used on steel or as a primer beneath paint on some substrates, and plain paint lacks the protective chemistry and adhesion benefits of a chromate coating on aluminum. Chromate coatings in general describe the family, but Alodine is the standard, specific method used here.

Alodine, a chromate conversion coating, is used after cleaning aluminum crankcase and accessory gearbox parts. This coating chemically bonds to aluminum to form a thin, durable protective film that blocks moisture and salts and provides an excellent surface for primer and paint adhesion. It’s the preferred corrosion protection step for aluminum alloys in overhaul work because it both guards against corrosion and improves paint adhesion, which isn’t as effectively achieved by applying paint alone or by other coatings intended for different metals. Zinc phosphate is typically used on steel or as a primer beneath paint on some substrates, and plain paint lacks the protective chemistry and adhesion benefits of a chromate coating on aluminum. Chromate coatings in general describe the family, but Alodine is the standard, specific method used here.