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Engine Anodes and Electrolytic Reduction

After two weeks of intense work on the Monitor’s vibrating side lever steam engine, we shifted efforts towards preparing it for electrolytic reduction treatment over the next three months.

Electrolytic reduction is a conservation treatment for metal artifacts in which the object is connected to the negative side of an electric circuit, called the ‘cathode’. Modern metal ‘anodes’ are placed close to, but not touching, the artifact and are connected to the positive side of the electric circuit. Once the tank has been filled with water containing a chemical called an electrolyte that allows electricity to pass through it easily, low-voltage DC power is turned on and the rust and corrosion on the engine begin to be chemically reduced by the flow of electrons. This makes the corrosion and concretion easier to remove and will help make the engine easier to take apart. Electrolytic reduction also has the effect of speeding up the release of chloride salts which have built up over the 140 years the engine spent in the Atlantic Ocean, definitely a good thing! Click here for an animation of the electrolytic reduction process:

Over the past week, we fabricated anodes for the Monitor’s engine using a combination of long lasting 316 stainless steel expanded metal mesh, and loops of platinum-niobium wire. These were suspended by a system of cables and wires which allowed us to follow the shape of the engine and provide treatment to as many areas as possible.

After installing the anodes and wiring the engine for electrolysis, conservators thoroughly cleaned the engine tank and filled it with approximately 35,000 gallons of reverse osmosis water. During the filling process, conservators also added approximately 250 pounds of sodium hydroxide (NaOH) to act as an electrolyte and bring the pH over 12.

This morning, Eric turned on the DC rectifier and electrical current is now flowing through our electrolytic reduction setup. We will closely monitor this process over the coming weeks and months before we get back into the engine tank in spring, 2011.

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