Corrosion protection
What is temporary corrosion protection?
Temporary protection of metals against corrosion is a process that protects an object from the occurrence of corrosion for a specified period of time. Temporary anti-corrosion protection requires the use of various types of protective substances (e.g., greases, oils, solutions, or emulsions). Specially manufactured modern anti-corrosion protection agents are also put into use. The most popular methods for applying anti-corrosion protection include spraying, dipping, and painting. Temporary corrosion protection can be removed after a certain period of time by mechanical methods or by washing.
Temporary protection against corrosion includes various types of substances applied to metal surfaces or non-metallic protective coatings. Their task is to provide an easily removable layer on the surface that protects the metal from corrosion for a specified period of time.
Temporary anti-corrosion protection of metals – applied agents
The agents used for the temporary protection of metals against corrosion are primarily preservative oils, which are mineral oils with appropriate additives. Solvent-based preservative oils are also used, as well as hydrocarbon greases or those containing a soap thickener. All these agents are so-called preservative greases.
In the process of providing temporary corrosion protection, solvent-based preservative greases are also used. Solutions of waxes or lanolin with a package of chemical additives also play an important role. Synthetic substances that create a thin or ultra-thin film are used as well. Frequently, these are special anti-corrosion packaging with corrosion inhibitors based on a solvent (corrosion and oxidation inhibitors, dyes, wetting agents, and thickeners). Aqueous emulsions with a preservative agent are also utilized.
Corrosion protection – modern technologies
Many products available on the market utilize modern technologies that provide coating durability and resistance to moisture and corrosive vapors, even under continuous exposure. Importantly, modern anti-corrosion protection agents do not require thorough surface preparation before the application of protective measures.
In addition, “more classic” anti-corrosion protection agents based on mineral substances are also available. These include various types of emulsifying anti-corrosion oils, which contain high-value corrosion inhibitors that perform well in industrial conditions. Agents of this type do not contain water. They are diluted with mineral oil or an organic solvent.
Universal anti-corrosion oils also represent an interesting solution. They often incorporate mineral oil raffinates with a suitable combination of refining additives. Products of this type perform well for the temporary protection of industrial goods and for safeguarding internal systems. Protective oils produced on the basis of noble mineral oil raffinates and chlorine-free solvents are available for purchase. Some protective agents are diluted with white spirit, which, after the solvent evaporates, leaves a transparent, very thin protective layer.
Manufacturers also offer thixotropic preservatives which, after the evaporation of the chlorine-free solvent, form a plastic, brown, and transparent oily coating. If necessary, these types of agents can be used in all climatic conditions. After the evaporation of the chlorine-free solvent, the colloidal solution forms a thick transparent coating that is resistant to mechanical damage due to its elasticity. Thixotropic agents perform well for long-term protection of items stored outdoors.
Methods of corrosion protection: spraying and painting
The spraying method is used for the preservation of large parts that cannot be immersed in a tank containing the preservative agent. The agent is sprayed using a special gun at a spray pressure ranging between 2 and 3 bars. Depending on the technology, spraying is performed cold or hot. Very often, the preservative agent is sprayed using an atomizer based on carbon dioxide or chlorine-free freon (HFC). This method is utilized for the ad-hoc preservation of components. The thickness of the layer depends on the number of coats applied.
The advantages of spray technology primarily include the uniformity and tightness of the coating. Therefore, in practice, two or three protective layers are applied. In turn, painting can be performed manually or mechanically. The manual method is based on applying the protective agent using a soft-bristled brush. Depending on the adopted technology, the anti-corrosion protection substance is also applied cold or hot.
Corrosion protection by the immersion method
In the case of the immersion method, the preservative agent is placed in a special tank, into which the object is then dipped. Subsequently, it undergoes draining, centrifuging, solvent evaporation, and cooling. The immersion method is very often utilized for preserving small-sized objects.
Many immersion method technologies involve heated tanks—this is known as hot preservation. The components to be protected are poured into a special basket, which is then submerged in the tank containing the preservative. Very often, appropriately designed feeders are incorporated into the immersion process. The immersion time usually ranges from 2 to 10 minutes. This duration largely depends on the properties of the protective agent and the size and dimensions of the objects being secured. If it is necessary to provide inter-operational and short-term protection, the cold method works better. The hot method is used if long-term preservation of details is required.
There are many advantages resulting from the use of the immersion method. Above all, attention is drawn to the penetration of the preservative agent into all open parts of the components. Uniform coverage of the surface is also significant. The immersion method is most commonly used for applying agents that provide a thin or ultra-thin layer.
Removing temporary protection
The protective layer of temporary anti-corrosion security can be removed mechanically through peeling, abrasion, or scraping. An effective method is also washing with aqueous organic solvents, both cold and hot. Often, washing with aqueous detergent solutions is also employed. The surface to be cleaned can be subjected to steam at low pressure. Temporary protection agents that form an ultra-thin layer on the metal surface are frequently not removed before subsequent processing.
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