You are looking at a spare connecting rod bearing recovered from the Titanic wreck site by the  RMS. Titanic  Inc. in June 1993. As Shown  at the right, the bearing linked a rod extending down from the piston with a rod coming up from the crank shaft. Essentially. the bearing help "translate"  the pistons up and down motion into the circular action of the crankshaft which turned one of the ships propellers.
 The Bearing weighs 2 tons and is more then 6 feet tall. a similar part in a car has the diameter of a tennis ball.  this particular bearing was on board the ship as a spare: the bearing  actually used remains buried under tons of debris in the north Atlantic.

 The bearing is sitting in a solution of 3%  sodium carbonate in water. A low voltage electrical current enters the water though titanium pins resting near the bottom of the tank. The current activates the carbonate, which attacks corrosion and caused rust to slowly fall off the metal. This first stage of treatment will take about 10 months