Causes
Corrosion of steel underground pipes is a phenomenon, the main cause of which can be called the electrochemical oxidation of metals from their constant interaction with moisture. As a result of such reactions, the composition of the metal changes at the ionic level, becomes covered with rust, disintegrates and simply disappears from the surface.
The oxidation process can be influenced by the nature of the fluid that flows through the underground heating pipeline or the properties of the environment in which it is located. It is for this reason that when choosing the appropriate means to combat rust, it is necessary to take into account all the features that preceded its occurrence. Otherwise, repair by welding is inevitable.
Application of rust inhibitors for closed systems
Corrosion-related processes that lead to the destruction of materials and structures can be stopped in several ways. Where it is difficult to technologically create a coating with a protective effect or apply an electrochemical method, inhibitors are used.
An inhibitor, or a substance that, when introduced into an aggressive environment, can slow down or completely eliminate corrosive infection. Very often, rust inhibitors are used where the medium is little updated or does not have a very high volume:
- tanks;
- cooling and heating systems;
- steam boilers;
- tanks with chemicals.
The effectiveness of the use of neutralizing substances is determined by these parameters:
- a rust inhibition index that compares performance without and with an inhibitor;
- protective degree;
- the amount of substance that provides the greatest protection.
Draw your own attention! The choice of a neutralizing additive is influenced by the composition of the medium and the protected material itself, the physical parameters that determine the course of the process.
Specification Options
Rust inhibitors are divided according to several indicators:
- according to the type of medium into which they are introduced: neutral, acidic, alkaline media;
- according to the mechanism of influence: passivating, adsorption;
- by type of protective action;
- by chemical features: volatile, organic, inorganic.
For neutral media, sodium nitrate, phosphates, and chromates are used. Sodium nitrate is used as an anode inhibitor, which makes it possible to protect steel in the water mass, and as a protection for copper and zinc. The non-toxicity of phosphates makes it possible to use them in cooling systems, industrial water supply. Chromates are suitable for protecting most metals.
Important! Phosphates and sodium nitrate are introduced in a strictly defined amount: if their concentration in the environment is erroneously calculated, they will have the opposite effect and increase the rate of metal damage. Acid rust neutralizers (amides, amines, their derivatives) are used in such cases:
Acid rust neutralizers (amides, amines, their derivatives) are used in such cases:
- metal surface etching;
- cleaning of hardware;
- protection of pipes, oil equipment and gas fittings.
With the help of such inhibitors, the efficiency of current sources that operate in chemical processes is often increased.
The action of alkali rust inhibitors is excellent in such applications:
- alkali treatment of amphoteric metals;
- protection of evaporator equipment;
- reduction of spontaneous discharge of current sources.
Inhibitors can act as anode or cathode. Anode adsorbed in the form of a film to protect the surface of the substance. These can be organic compounds and surface-energetic compositions. Cathode also somewhat make the surface of the cathode smaller and make less cathode current, but they are not highly efficient.Very often, a mixed version is used, which reduces the rate of both cathodic and anodic destruction.
Thermal media additives
The issues of protecting such systems as heat supply from the influence of rust are relevant, since actually ignoring them often leads to accidents. What to choose as a rust inhibitor for heating systems depends on such factors:
- temperature performance indicators;
- type of equipment for the boiler room;
- pumping equipment;
- system material.
The key filling of heating systems is water, which requires the stabilization of thermophysical parameters, reducing the formation of precipitation and scale.
Due to this, substances that help sedimentation do not need to be applied. Not one substance is changed, but a set that lowers the freezing point of water, reduces scale deposits, and slows down the dissolution of rubber gaskets on fittings. A complex of additives for heating systems - antifreeze. These fluids smooth out the negative effects of the heat carrier.
Important! Antifreezes contain hazardous substances
Physical reagentless water treatment
As the name implies, this group of devices operates without consumables. Some of them use electricity to work, others do without it. This category includes many devices that can be divided into groups:
- permanent magnets;
- electromagnets;
- electronic;
- electrolytic;
- electrostatic.
All of these devices effectively change the behavior of water. When using these devices, the level of deposits is reduced or the interval between system cleanings is increased. Some of the devices are even capable of removing existing deposits from the system.
Essentially, physical scale inhibitors, whether magnetic, electrolytic, or electronic, work in a similar way, changing the behavior of natural salts in water so that they remain in solution rather than on the pipe walls.
permanent magnets
The simplest of the devices of this class. It is a group of permanent magnets connected to each other. The water passing through the device is treated with a magnetic field. The magnetic field causes the water to build up electrostatic charges, which causes temporary changes in the shape of the salt crystals. It changes their shape from a conventional cuboid to a needle-like structure that is more prone to leaching out of the system than sticking to surfaces.
It does not require power or consumables to operate. The device crashes into the system. There are developments that are installed on a pipe without tie-ins into the system.
Models are selected according to the diameter and flow of water. There are restrictions on water temperature.
Electromagnetic systems
Similar to systems with permanent magnets, but have a stronger magnetic field and last longer. Usually must be installed very close to the boiler, as they only process the water flowing through them. If the flow stops, the accumulation of water charges will stop until the movement of water starts again.
Unlike magnetic systems, these systems can operate at high water flows and at higher temperatures, however, they are more expensive than magnetic systems and require thorough cleaning of the outer surface of the pipe at the installation site.
Electronic systems
Electronic water treatment systems are distinguished by the fact that their operation does not depend on the flow rate of water. A high-frequency signal affects the water at the molecular level using a device installed on top of the pipe. The impact on water is 24 hours a day in both directions, upstream and downstream of the water, simultaneously treating all the water in the system.
The high frequency radio signal changes the crystallization characteristics of the salts in the water, preventing the formation of new deposits.
Some devices in this group are able to remove old deposits and cause a passivation effect in pipe metals, preventing corrosion.
Permanent magnets Electron. electrolyte systems. systems
Electrolytic systems
A small electrical current passing through the water effectively changes the molecular structure of the resulting deposit crystals, preventing the formation of hard deposits on boilers and pipes. This system modifies the physical properties of the ions, but no chemical reaction occurs. In an aqueous solution, calcium, magnesium and some other salts are partially ionized and therefore are affected by an electromagnetic or electrostatic field. Increasing the degree of ionization of the ions in the solution reduces the formation of deposits.
Electrostatic systems
The kinetic energy of the moving water stream creates a charge that is transferred to the water. This breaks the stability of particles in water, which are in equilibrium, having equal charges. By neutralizing the charges and disturbing the equilibrium state of the mixture, the device causes the particles to precipitate, entraining substances that can form scale. The device causes early, uncontrolled precipitation of small, incompletely formed crystals. In this way, hard deposits are prevented and soft sludge is flushed out of the system.
