| Condenser is not only one of linchpin equipments in cooling water system of power plant, but also the most important assistant equipment of turbo generate system. The quality of condenser is very important to the security and economical running of the power plant. Many power plants at coast area use seawater as condenser cooling water with the increasing demand of electric power and the shortage of fresh water. Nowadays, more and more condensers made by titanium tube are used by power plants at coast area, because titanium possesses the quality of excellent corrosion-resistant ability, high specific strength and well colligation performance. However, there is a fierce trend of Ti/Fe galvanic corrosion in the titanium tube condensers which use carbon steel as their water-room. Usually, the trend is reduced by painting and sacrific anode cathodic protection. But how to control the potential of the joint at -0.80V is a big problem. If the potential is more positive than -0.80V, the steel will not get enough protection, but if the potential is more negative than it, there will be hydrogen embrittlement on titanium tube. To solve this problem, a new method of cathodic protection is raised in this thesis, which is electrical current adjustable sacrific anode cathodic protection. This method can control the protective potentials of carbon steel and titanium separately at the same time, can adjusts the potentials with the time and polarization condition, too.To exploit the electrical current adjustable sacrific anode cathodic protection, the thesis studies the rate and mechanism of condenser with carbon steel room and titanium tube, as well as the effect and the feasibility of electrical current adjustable sacrific anode cathodic protection are carried out. The Finite Element Method (FEM) method is used to calculate the potential distribute in the condenser. Mainly work as follows:First of all, different surface area of steel (Q235B) and titanium (TA2) are chosen to compose the galvanic couple. The rule of corrosion of this galvanic couple with the area ratio of Ti/Fe changed from 1 to 1000 in the still and normal temperature seawater was studied by the method of weight-loss and measuring the galvanic-current and galvanic-potential associate with the polarizing characters of this two metals. Then the galvanic-current and galvanic-potential of galvanic couple in different temperature and different velocity of seawater were measured. The results show that the corrosion rate of anode is increased with the increasing of the area ratio of cathode verse anode, the temperature and the velocity of seawater. But there is a limited area ratio number. The corrosion rate of anode does not increase when area ratio of cathode verse anode is more than the limited area.In order to obtain the equivalent circuit of the protection system and other parameters such as galvanic-current changing with time and the potential distribution in condenser, especially in the titanium tube, a condenser model was designed based on the representative structure of titanium tube condenser. Polarization characters of titanium and carbon steel at -0.80 were studied. The results show:(l) with the electrical current adjustable cathodic protection, the range with the trend of hydrogen evolution near the joint of this two metals for titanium is short (shorter than 10cm) and the steel water-box was protected well, which is the confine of titanium tube with the trend of hydrogen evolution is reduced effectively and the carbon steel was protection well when we are using the new method of cathodic protection; (2) the formation of calcium magnesium deposit was one of the most important factor to cathodic polarization process; (3) rp ,rf ,rawere calculated when the polarization of model system were stable according to the equivalent circuit; (4) the result which is calculated by FEM is consistent well with the data which were got from the experiment, so we can draw the conclusion that the physical chemical model is reasonable.
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