Research On All Solid-state Reference Electrode Used In Deep Marine

In the industry of marine exploration, there are many subsea metal structures. Corrosion monitoring is the most important of safety monitoring. In cathodic protector system for subsea metal structures, measuring electrical chemistry parameters is needed. It is necessary to have a reference electrode that is exact and stability. Due to the changes of pressure and the complicate properties of marine environment, nowadays, Ag/AgCl reference electrode often is used in electrical chemistry measurement, which is regarded as the best reference electrode. However, the Ag/AgCl reference electrode bought from market cannot be used for cathodic protector system and marine environment for a long time. In this paper, in order to deal with the problems of reference electrode used now, a Ag/AgCl all-solid-state reference electrode was studied, according to the conditions of deep marine environment. The results show that the reference electrode studied is characteristic of precision, stability, and enduring high pressure.In order to endure the high-pressure of deep marine, the reference electrode was made by using Press Powder Method. The main part of reference electrode composed of pure silver powder and silver chloride powder was made by high pressure. The effect of the pressure of pressing the electrode was studied, the result of which shows that when the pressure is between 1T/cm2 and 10T/cm2, it did not effect the properties of electrode. But in order to simplify the manufacture and endure the high-pressure, high pressing pressure, 10T/cm2, was chosen. When the percent content of AgCl is less than 20%, masses of Ag bring on quite difference of electrical potential. When the percent content of AgCl is more than 70%, superfluous AgCl did not conduct electricity. When the percent content of AgCl is between 20% and 70%, the properties of electrode had not changes obviously. Silver chloride powder was made by solid-phase reactions at room temperature. Their structure and particle size were characterized with SEM. It was found that the particle size is 2～3μm. The very small powder can increase the active center of electrode surface and enhance the electrical chemistry properties of reference electrode. Ag/AgCl all-solid-state reference electrode studied had good properties such as long stability in seawater, Nernst response property, temperature response property and antipolarization. Electrode potential drifts±0.5mV for long time test. Because there are many ions in seawater, the effect of these ions to electrodepotential must be studied. The result shows that Br－ can make the electrode potential decrease and still remains stable for a long time, and SO42－ cannot affect the electrode potential apparently. At the same time, according to simulate the real conditions of using the reference electrode in marine, the relationship between velocity and electrode potential was studied by using the analog testing equipment. Additionally, The result shows that the influence of seawater flow on the electrode potential is slight when the velocity is less than 5m/s. The simple kinetics parameters of reference electrode were measured by using Electrochemical Impedance Spectroscopy (EIS). The result shows that the reference electrode is characteristic of reversible electrode.Ag/AgCl all-solid-state reference electrode studied has applied for invention patent, and the number is 03138856.6. At the same time, the mould that making electrode has applied for applied new type patent, the number is 03271344.4. Ag/AgCl all-solid-state reference electrode studied will be applied in 863 project, the technique of detecting cathodic protection potential without touch. It will be made into the probe for corrosion monitoring and be used to monitor the corrosion potential of seabed pipes.