Application and research overview of impressed current cathodic protection for submarines

The basic principle of cathodic protection is to add a certain number of electrons to the protected metal card, so that the protected metal becomes a cathode and is protected.

2. Research overview at home and abroad

The characteristics of the impressed current cathodic protection is: follow the change of external environment such as different area, such as temperature, salinity, the wind and waves, and the attitude of the message the change of the premise, the potentiostat can according to the reference electrode signal, automatic adjustment protection current, make the hull is always in good state protection, is conducive to shorten the dry-dock date, dock delay progress of distance, save fuel and coating.

3.1 Preparation of pt/NB composite anode

At present, the applied current cathodic protection system is usually designed to have an effective service life of 5 years, while the service life of the system has been designed to be more than 20 years in foreign countries, which is almost the same as the life of the ship. To adapt to this service life, it is necessary to have a good auxiliary anode, potentiostat with high function, reference electrode and anode screen material. The methods of providing current can be divided into impressed current method and sacrificial anode method.

In the past a long period of time, the submarine hull erosion is severe, this is due to the early our submarine only sacrifice anode to protect the pressure shell in the ballast tank, but not the pressure tank shell only paint coating protection, not the use of cathodic protection measures, the shell of severe erosion.

Platinum is the ideal anode material, but it is very expensive, can not use pure platinum as the anode material, only thin platinum attached to the base material, there are three kinds of base materials: titanium, tantalum, niobium.

Seawater containing chloride ion is high, high electrical conductivity, dielectric is very strong, so the ship in seawater erosion is more serious, the submarine is like other ships, in seawater erosion dielectric, if do not take appropriate corrosion protection measures must be under severe erosion, especially the submarine's premise is more demanding, higher requirement for corrosion protection. About using sacrificial anode to protect submarine, the us navy raised at different points of view, they think that the submarine to reduce weight, with a large number of sacrificial anode is limited by a lot of, against the sacrificial anode in the shell, thought after the shell with sacrificial anode, sailing sound it produces can be measured, influence its concealment, As for the resistance caused by the sacrificial anode on the hull, some tests have been carried out. 18kN), but not much at low speeds. In the early 1970s, a number of submarines were laid up one after another. In a short period of one year, the steel plates were eroded and perforated more than ten times respectively, which greatly increased the dock repairs and seriously affected the combat readiness of submarines.

3.2 Research on high functional anode plate material

In order to make the thin platinum (about 10μm) and the matrix have a certain strength of bonding, the developed anodes can last more than 20 years and the discharge rate of a single anodes is more than 50A by vacuum deposition and drawing technology.

This is an important topic for conventional submarine, because is used to protect the power consumption of is are closely related to the endurance of the boat, if the maximum protection current navigation (descend) is about 72 a, output voltage can be around 8 v, such as diving, the instantaneous maximum power consumption about 600 w, follow descend after the extension of time, the hull of potential polarization, The required current and output voltage should be reduced, the reduced value is related to the paint condition and speed of the boat, the submarine is in the cruising state for most of the time, the fruit of the water area is less, the current required for impressed current protection is about 10A, the voltage is 5 ~ 8V, the required power is about 60W. The impressed current method is the addition of a DC power supply, the positive electrode of the power supply is connected to the auxiliary anode, the negative electrode is connected to the metal to be protected. Titanium is the cheapest, but its breakdown voltage is 8 ~ 12V, the use is limited, tantalum breakdown voltage is high & GT; 100V, but it is too expensive, only the breakdown voltage of niobium above 80V can basically satisfy the application under various conditions, but also relatively cheap, the hub in the manufacturing process, platinum layer and matrix composite method, methods are electroplating, welding, vacuum, deposition, rolling, drawing, explosive composite, etc.

Impressed current cathodic protection technology has been successfully used in some old submarine, which is mainly used to protect the non-pressure hull and propeller, while sacrificed-anode protection is still used for the permeable section of the superstructure in the ballast tank and the wall of the command platform.

3.3 Power required to protect the system

The commonly used epoxy putty anode screen material abroad is called "permanent" anode screen material. It has long life, simple construction, and can be formed in one time. It has important significance for the protection potential distribution is average, and the ideal potential distribution can be obtained by installing fewer anodes.

The mooring test and sailing show that the applied current cathodic protection system can automatically adjust the required protection current according to the different states of the submarine (berthing, sailing, diving, rising and different speed), so that the submarine is always at the given protection potential.

The commonly used cathodic protective paint in China is green epoxy enamel, which has low cathodic potential resistance and harsh and inconvenient construction requirements.

The U.S. Navy currently uses impressed current protection systems to protect against erosion, including a significant number of large, high-speed transport vessels built by Japan. From the dock inspection to see the erosion prevention effect is ideal, paint peeling place is not yellow spots, shiny black, no rust traces.

Foreign research on submarine corrosion prevention has been reported as early as in the 1950s, and at that time it was still mainly using the technology of sacrifice anode and coating.

The late 50 s, the us navy started in the submarine long the impressed current cathodic protection test, from the report, the U.S. navy nuclear submarine "sea Wolf", "fishing" used the impressed current cathodic equipment automatic control, several years later, was confirmed by several docking corrosion effect is obvious, no significant rust layer, underwater branch pits are not found in steel plate, The weld is basically intact without corrosion, and the shell plate is relatively smooth, which has achieved good protection effect. Sacrificial anode method is to use a kind of potential is more negative than the protected metal metal with the protected metal together, rely on the more negative potential of metal continually dissolve erosion of electronic method to protect the protected metal, this in order to protect the rest of the metal and its erosion of metal called sacrificial anode, commonly used sacrificial anode metal zinc, aluminum, magnesium, and other alloys. In some countries, ships equipped with impressed current cathodic protection can be docked for a distance of 2.5 years.

2) Provide reference electrode for signal and measurement of hull potential;

1) An insoluble anode that is electrified and strictly insulated from the boat body;

The external current cathodic protection is a new technology which is used to prevent the erosion of underwater department according to the electrochemical principle. The impressed current cathodic protection device is composed of three departments.

The quality of the anode screen material has a direct impact on the use function and protection effect of the system. The anode screen material is required to be resistant to seawater and chlorine gas, and the cathode potential is high, and the construction is convenient.

3) Automatic control of power supply equipment? Potentiostat.

3. Research content and technology hub

The design life of the submarine impressed current cathodic protection system can be the same as that of the ship (more than 20 years) at the current development level. The main parts do not need to be replaced, and the dock repair distance can be extended. The dock cost and workload can be reduced greatly.

Cathodic protection has a long history. In 1824, the British installed zinc plates on a ship for cathodic protection.

Application and research overview of impressed current cathodic protection for submarines

At present, the corrosion protection of foreign naval submarines has been corresponding to the specification. The corrosion protection of submarines is coordinated with the coating, and the cathodic protection is coordinated with the impressed current of the sacrificial anode. The sacrificial anode is used to protect the ballast tank, and the structure of the submerged area in the wall of the command platform. It is practical and effective for submarine to use impressed current cathodic protection to protect the whole submersible hull and propeller.

There are many foreign large warships and submarines using impressed current protection, but there is no report that impressed current cathodic protection system can cause significant interference to the electronic equipment on board and affect the missile system.