Cleaning Bristol Blenheim BL-106 rudder pedals for painting

Suomeksi

https://www.ilmailumuseoyhdistys.fi/blogi/2025/12/10/49878Once the pilot's seat of the Bristol Blenheim BL-106 had been restored, we continued our work on the rudder pedals. The pedals themselves are not broken; but they are heavily soiled and the aluminium parts already display corrosion-induced pitting. The steel parts of the controls are covered in rust.

This time, we began the restoration by investigating how the rudder pedals had originally been surface-treated. It seemed that the aluminium parts of the pedals were simply bare aluminium. Their surface was distinctly greenish yellow. There were also traces of grey paint found on the surface of some parts.

We consulted the Finnish Air Force Museum about the colour of this aluminium. It turned out that the aluminium parts of the rudder pedals were zinc chromated. At the same time, we asked if it was possible to determine from the serial number (50966/1), stamped on the surface, whether the pedals were manufactured in England or Finland. The serial number revealed that these pedals were made by the Finnish State Aircraft Factory (Valtion lentokonetehdas). After the serial number, there was also a small VL logo.

The interior surfaces, seats, and controls of the cockpits of Blenheim bombers, manufactured or overhauled in Finland, were painted with VL’s standard grey paint in the RAL 7005 shade. Thus, the remnants of grey paint found on the rudder pedals of the BL-106 confirmed that the same practice had been applied to this particular aircraft. However, most of the original surface paint had already worn away.

We will paint the rudder pedals with Isoguard Pansar paint for metal surfaces, in the RAL 7005 grey shade. This paint is alkyd and linseed oil based. Before applying the grey topcoat, the steel parts of the rudder pedals will be treated with clear Isotrol lacquer. The aluminium parts will be painted directly with Isoguard Pansar paint. This was also the method we used when restoring the pilot’s seat.

We began cleaning the rudder pedals of dirt, rust, and grease. The rusted steel components were mainly cleaned by mechanically grinding their corroded surfaces until they were clean. When cleaning the dirty surfaces of the aluminium parts, we first tried both Sinol and white spirit, but these were ineffective. We had to find a more suitable solvent.

We proceeded to use both Solmaster Painter's Solvent and CRC Brakleen Pro brake part cleaner. We applied these products to the various components, spreading the solvent onto the surface and into crevices with a brush. The solution was left to work for a while. After that, the surfaces were scrubbed using both soft brass and plastic brushes, and for tight gaps, even toothbrushes. A steel brush was not used, as it would have damaged the zinc chromated surface of the rudder pedals. After scrubbing, we wiped the surfaces with a cloth. The solvents proved effective at removing the sticky grease and dirt, although the treatment had to be repeated several times.

A small steam cleaner was also put into use. The surfaces were treated again with the solvents mentioned earlier and then "blasted" with the steam cleaner. The steam cleaner was very effective at removing grease and dirt, but it was not sufficiently effective against oxidised areas. After each steam cleaning, the part was wiped clean with a cloth. By repeating this method, the surfaces gradually became cleaner, as each time more dirt and remnants of old paint were removed.

After using the solvents and the steam cleaner, patches of wear caused by corrosion remained on the surface of the rudder pedals. The corrosion had already broken through the zinc chromated surface of the aluminium components, leaving them mottled. These worn areas were rough to the touch. We considered whether to leave them as they were or to sand them smoother.

Photo: Jouni Ripatti

We decided to sand them so that the corroded spots would be as inconspicuous as possible beneath the new painted surface. The corrosion patches were sanded with a scouring pad, which worked well. The more severely corroded spots had become so rough that they were carefully “carved” smooth with a thin-bladed utility knife. In this way, the corroded areas were made sufficiently smooth for painting. The rudder pedals of BL-106, mottled by corrosion, were now ready for painting.

Photos: Lassi Karivalo, unless otherwise mentioned

Translation to English: Erja Reinikainen