Efficient Cathodic Protection of Stainless Steel Small Bore Tubing

摘要

Cathodic protection of stainless steel can be obtained at far more positive potentials than carbon steel. A side effect of this is that the cathodic current density requirement of stainless steel is normally less than 5 % of that for carbon steel. This again has lead to an efficient method of cathodic protection of stainless steel seawater piping systems and seawater heat exchanger tubing, utilising the principle of resistor controlled cathodic protection. In the present paper the ability to protect small bore tubing is demonstrated by laboratory tests as well as by calculations. Furthermore, the well known “rule of thumb” saying that the internal protection is limited to 5 x the internal pipe diameter, is shown not to be valid for stainless steel tubes for which protection is obtained for more than 100 x internal diameter. Successful application to a small bore tube heat exchanger is also demonstrated.