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February 24, 2020

In the previous post, we covered general rust protection for homebuilt or amateur-built aircraft. To advance the discussion, this post covers the specific measures to take for protecting different parts of a home assembled plane. Find out how to protect specific aircraft parts like engine mounts, gas welded steel fuselages, control cables and exhaust pipes from rust.

Gas welded steel fuselages

A protective coating of linseed oil works to protect the interior of a tubular steel fuselage from rusting. After the welding work is completed, flush the interior of the tubular structure with linseed oil, preheated at 160° Fahrenheit.

Rotate the steel fuselage to ensure no part is left uncoated.

Drain the excess oil after a couple of minutes. Plug each hole after the oil is drained out using self-tapping cadmium plated screws. This prevents moisture from accessing the steel fuselage again.

For optimal protection, consider sandblasting the gas welded structure.

Sandblasting technique is very effective for cleaning and degreasing welded steel parts like tubular steel fuselages and engine mounts.

This process involves subjecting the parts to a blast of an abrasive. Sand is typically used as an abrasive. Glass beads may also be used.

Prime the sandblasted parts to prevent rust from recurring. Also, consider outsourcing the ‘messy’ sandblasting operation.

Engine Mount

By the time the engine is installed, the engine mount will have degraded to the point of requiring rust protection. Consider painting the landing gear and the engine mount with an epoxy primer and paint.

Epoxy coating is rough and durable. It inhibits ordinary solvents from disrupting the finish.

A top coat of lighter color makes it easier to inspect the surface for cracks.

Control cables

Apply grease or oil to protect carbon steel or stainless steel control cables. Do not paint the control cables.

Corrosion of dissimilar metals

When two different metals come into contact with each other, the moisture causes a weak electric charge to run from one metal to the other. This oxidizes the weaker metal, causing the surface to corrode.

For instance, you may have to use steel washers, bolts and nuts in an aluminum aileron bellcrank installation.

Apply a coat of zinc chromate primer on surfaces of both the metals to treat the corrosion. For a temporary solution, you can consider spraying WD40 or rubbing grease or oil.

While the bolts are cadmium-plated to offer some degree of rust protection, it’s common for the plating to scrape off during installation, leading to metal-to-metal contact.

Moisture plays its part, causing accumulation of snow-like powder on the aluminum parts.

Metal-to-wood contact

Protect metal parts that are in contact with wood using a coat of zinc chromate primer followed by a finish coat of paint.

Treating the wood with a coat of polyurethane varnish prior to its installation also helps. When it’s installed, apply varnish on each contact surface. The bolts may also be dipped in varnish prior to installation.

Exhaust pipes

Stainless steel exhaust pipes don’t need protection from rust. On the other hand, if the exhaust pipes are made using mild steel, they are prone to rust. Consider sandblasting and then painting the pipes using hi-heat resistant paint.

Follow the manufacturer’s instructions for getting the best results.

Acorn Welding is Canada’s largest aircraft exhaust and engine mount company. Today, with a modern 50,000 sq.ft. facility, forty full-time staff, almost 100 new manufactured products, aircraft exhaust and engine mounts for over 50 makes and 270 models, and 750 fabrication fixtures, Acorn Welding continues to grow. Contact Acorn Welding today.