This invention relates to apparatus for plating inner surfaces of tubular members which is suitable for use in applying chemical plating to the inner surfaces of the tubular members. 
An example of the prior art for applying chemical plating to inner surfaces of tubular members, Japanese patent application laid-open No.  45495/79 (corresponding to U.S. Ser.  No.  820,797) discloses the art of applying copper plating to zirconium tubes.  The problems encountered in applying chemical plating according to the prior art to the inner surfaces of the tubular members could be summarized as follows:
(1) When a chemical plating method is adopted, deposition of the metal to the surface of the plated member takes place more slowly than when an electro plating method is used.  Thus, when the large number of tubular members to be individually treated, the plating operation would be necessary long time. 
(2) As a chemical plating operation is carried out over a prolonged period of time, a rotor and shaft of a plating solution circulating pump undergo deposition of metal by reducing reaction, and these parts would be subjected to a high friction during rotation.  When this phenomenon occurs, it would be necessary to stop the pump after a continuous operation is performed for about 5 or 6 hours. 
The pump thus stopped must be overhauled and its parts must be cleaned.  When copper plating is applied, cleaning of the parts must be polished with concentrated nitric acid.  When plating is applied simultaneously to the inner surfaces of a plurality of tubular members, and the number of pumps used is equal to the number of tubular members to be treated, a lot of labor would be required for performing a pump cleaning operation and the plating operation efficiency is applied would be greatly reduced.  Moreover, this might cause variations in the quality of the coating applied to tubular member and in the thickness of the coating.