The transition from wooden shipbuilding to metal shipbuilding provided known advantages, but led to new problems. Seawater in the form of liquid and aerosol is a highly corrosive medium that can damage and destroy metal parts. Over time, ships become covered with rust, which must be dealt with. Fortunately, there are several basic methods of corrosion prevention and treatment available and are actively used.
Naval problems
Recently, curious publications appeared in the American media on the topic of preserving and restoring the technical readiness of the US Navy ships. Despite all the successes of shipbuilders, corrosion remains a serious problem, which is costly to solve.
According to press reports, in 2014, the US Navy spent about $ 3 billion on rust removal and treatment of structures - about a quarter of all expenses on repairs of combat and auxiliary personnel of the fleet. It is noted that all ships and vessels suffer from corrosion, regardless of their design. Both steel aircraft carriers with a displacement of tens of thousands of tons and light aluminum boats require maintenance.
Corrosion control is carried out in several ways and in all conditions. Some of the measures are taken during construction or dock repairs; other techniques can be used for minor repairs by the crew directly during the hike.
Nevertheless, despite all the efforts of the crews and repairmen, the ships often do not look their best. Seams, corners, holes and other structural elements quickly become covered with a characteristic brown coating, and its removal on large ships turns into a continuous process. After work in one area, you have to move on to another, and so on without interruption.
It should be noted that all fleets of the world suffer from corrosion, incl. and ours. In fact, on any ship - especially after military service - you can find rusty parts and characteristic marks on the paint. The only exceptions are ships preparing for festive events. Their crews take all measures of a technical and aesthetic nature.
It is obvious that the fight against rust is a significant part of the Russian Navy's expenses for the maintenance of ships. However, exact figures of this kind have not yet been published in open sources. It can be assumed that the share of such expenses is not too different from American practice.
It should be noted that not only the ships themselves suffer from corrosion. External factors negatively affect the operation and resource of ship systems, weapons, carrier-based aircraft, etc. In all cases, rust prevention and control measures must be taken.
Rust theory
Warships, like other metal objects, suffer from corrosion due to external factors. Chief among them is salty sea water and its vapors. There are also other factors that can lead to rust, loosening and destruction of parts.
In general, it is customary to distinguish between three types of corrosion. More rare in naval practice is chemical corrosion caused by the action of certain substances on the metal in a dielectric atmosphere. More common is electrochemical corrosion, in which the metal is destroyed by the action of various chemicals and electric currents of different nature. The latter can appear due to leaks in ship networks (electrical corrosion) or formed due to the interaction of metals and other substances (electrochemical).
Rust foci are superficial, subsurface and intergranular. Damage on the surface is immediately visible, and subsurface damage leads to swelling of the metal, which also simplifies detection. Intergranular corrosion, which affects the crystal edges of the material, has no external manifestations and is the most dangerous.
In the early stages, corrosion results in brown spots and unsightly streaks. Then the damage to the metal begins to affect the strength of the structure. If you do not take action in time, you should expect the appearance of deep damage or even through holes in the metal - depending on its thickness. Loaded parts, losing strength, can collapse with the most serious consequences.
Problem prevention
Several basic methods of protecting a ship from rust are known and applied. They are constantly being improved, but the basic principles generally remain unchanged.
A radical solution to the problem is the use of non-metallic materials or alloys that are weakly susceptible to corrosion. Wood, plastics and composites of all kinds do not rust - although they do have other risks with prolonged exposure to salt water. Aluminum structures are also not protected from the negative effects of the environment, but they are more resistant to corrosion in comparison with the main grades of steel.
When using materials that are prone to corrosion, several basic protection techniques are used, both individually and in various combinations. Protection can be mechanical, chemical, electrochemical and electrical, and is performed using various means.
Protection against electrical corrosion is carried out by the correct construction of the ship's electrical systems, excluding leaks to the hull. It is also necessary to ensure the insulation of the case, which does not allow metal to come into contact with water. Electrochemical protection is based on the idea of changing the course of a reaction using special means. An example of this is protection with zinc coatings or bars on the outer surface of steel parts. When exposed to salt water, zinc is destroyed, but the steel remains intact.
Mechanical and chemical protection involves the application of paint and varnish coatings or the creation of oxide films on the metal surface in one way or another. In this case, contact of the metal with water and, as a result, the formation of rust is prevented.
Active struggle
It is impossible to completely and guaranteed to prevent the formation of rust, and therefore regularly have to deal with the existing damage to the structure. Such repairs can be both simple and complex, depending on the size and depth of the damaged areas.
If a rust center is found, it is required to clean the part to intact metal, and then treat it with a protective compound and apply a regular paint and varnish coating. During the voyage, these tasks can be accomplished with hand tools, and more sophisticated equipment is used at the docks.
It should be noted that getting rid of corrosion is not only difficult, but also expensive. According to known data, the US Navy is now using a two-component protective compound Ameron PSX-700 for treating brushed surfaces. A gallon of this mixture costs about $ 250 and is theoretically enough for 27 square meters. surface. At the same time, PSX-700 is considered not only effective, but also one of the cheapest means of its class.
The navies of other countries use other coatings and compositions for the same purpose with different cost and different specific consumption. However, the principles of repair do not change: rust removal, application of protection, painting.
Fight without end
Corrosion and destruction of metal structures is a major problem that requires constant attention at all levels. According to various estimates, rust annually destroys the equivalent of 10-15 percent in the world. total annual steel production, and developed countries have to spend up to several percent of GDP to combat it.
Together with other structures, the naval forces of different countries suffer from corrosion. At various stages of the design, construction and operation of ships, all necessary measures are taken, but it is impossible to completely exclude damage to the metal structure. And the characteristic drips on the surface of ships turn out to be far from the biggest problem.
Unfortunately, all existing measures can only reduce the likelihood of damage to ships from corrosion, as well as reduce its negative consequences - but not completely exclude it. A radical solution to the problem may be associated with the abandonment of metals in shipbuilding, but with the current development of technology, this is simply impossible. Therefore, the fight against rust will continue.
