CORROSION PROTECTION FOR METALS
When exposed to corrosion, especially oxidation, unprotected bare metal surfaces change the surface condition that has often only been achieved after considerable effort. This not only leads to a deterioration in appearance but also often reduces the optimal function.
Corrosion preventives serve to protect metal surfaces against the influence of the atmosphere in the broadest sense of the term and, thus prevent the conversion of metals into their compounds especially oxides.
In general, the application of an effective surface protection involves only a fraction of the costs that are incurred due to corrosion damage.
The extent of corrosion mainly depends on:
- the combination and pre-treatment of the materials (for example, malleable cast iron or grey-cast iron are especially sensitive to corrosion),
- the surface quality of the material (rough surfaces are more sensitive to corrosion than smooth surfaces),
- climatic influences, such as marine climates with a high saltwater content or tropical climates with a high air humidity and extreme temperature fluctuations trigger corrosion, as does the high SO2 air-content experienced in smog conditions,
- other external influences, such as aggressive exhaust gases, the effects of acid vapors from pickling baths, the contact effect of materials touching each other, residues from treatment processes, dust and hand perspiration during handling.
Basically, it can be distinguished between permanent and temporary corrosion prevention. Permanent corrosion prevention is, for example, ensured through the use of paint, galvanic coatings and enamel that can only be removed with difficulty using mechanical or specific chemical methods. Often, this is not possible without changing or damaging the metal surface. The corrosion protection products, sold under the brand name ANTICORIT, belong to the group of temporary corrosion preventives, although modern cavity protection will ensure a corrosion protection of up to 15 years. If needed, temporary corrosion preventives can be removed quite easily using solvents or suitable aqueous industrial cleaners without the protected surface being damaged.
CORROSION PREVENTIVE OILS
Corrosion preventives are available in a wide viscosity range adjusted to the technical requirements. They do not contain easily volatile components. In terms of composition and texture, the protective film produced during the application matches the oils used. An exception in this respect is the group of thixotropic corrosion preventives, the protective films of which display an increased higher apparent viscosity when at rest. This has a positive effect on the film stability on vertical surfaces and on the corrosion protection properties.
The different corrosion preventive oils are suitable for use in the surface preservation of semi-finished products, tools and spare parts as well as for the internal preservation of hydraulic systems, pumps, gearboxes and other systems. In addition they can also be used as greasing oils for thin sheets.
Their use is recommended for hall and shed storage as well as during transportation with suitable secondary packaging.
Temporary corrosion preventives can be easily removed using normal alkaline or neutral detergents and solvents. They are compatible with normal mineral oil based lubricants and may usually remain on the surfaces during the start-up of machines.
Multi-purpose oils are available for certain applications, for example, as test bed oils that take over the machine lubrication and then ensure optimum corrosion prevention or, as Prelubes, to protect thin sheet surfaces against corrosion and then, in the press, assume the function of a drawing oil.
SOLVENT-CONTAINING CORROSION PREVENTIVES
The solvent-containing corrosion preventives are a group of versatile products based on white spirits or isoparaffins.
By modifying the type and quantity of the non-volatile content it is possible to produce films of different thickness and quality levels. The available portfolio offers products with oily, vaseline-like greasy, wax-like and paint-like protective films. The choice of the adequate solvent type should be made by taking into account local regulations regarding volatile organic compounds.
Dewatering fluids are especially suited for the after treatment of parts that have gone through an aqueous treatment (machining operations using water miscible coolants, galvanic finishing or phosphatizing).
The use of suitable surface active substances leads to the separation of the water when the parts are immersed into the dewatering fluid. According to requirements, dewatering fluids are available that dry without producing films or that, in addition to the drying effect, also leave a corrosion prevention film on the parts. Customers have the choice between products that produce oily, grease-like, wax-like or paint-like films.
Dewatering fluids with rust-penetrating as well as wear and friction-reducing properties have been developed for specific applications, especially in the area of maintenance.
CORROSION PREVENTIVE CONCENTRATES
The corrosion preventive concentrates are used in dilutions with solvents, mineral spirits, isoparaffins and chlorine-free hydrocarbons (in suitable systems). They can also be used to improve the corrosion prevention of metal machining and function oils.By varying the concentration, different film thicknesses can be achieved leading to different corrosion protection times.
In water, the water-miscible concentrates produce transparent solutions or emulsions. They combine the benefit of water, as an environmentally friendly solvent, with excellent corrosion prevention. Their use is especially recommended when parts have gone through an aqueous pretreatment (metal machining using a water miscible coolant, galvanic finishing or phosphatizing) or when used as an additive to press water. According to requirements there is a selection of products available to produce strong, thermally stable emulsions with a good resistance to acidic or alkaline contaminants as well as concentrates for semi or meta stable emulsions for especially high corrosion prevention requirements. The complete drying of the emulsion films on the surface is necessary to achieve optimum corrosion prevention results.
CORROSION PROTECTION WAXES
The corrosion preventive concentrates are used in dilutions with solvents, mineral spirits, isoparaffins and chlorine-free hydrocarbons (in suitable systems). They can also be used to improve the corrosion prevention of metal machining and function oil. The use of waxy corrosion preventives is sensible when parts need to be protected from severe climate conditions, or protected for a long term. The different available wax-film types are covering the whole range from cavity protection till underbody coating, as well as long term protection under different storage conditions. Usually waxy types of products are pre-diluted in solvent or water for application reasons.
VCI (VOLATILE CORROSION PROTECTION) PRODUCTS
The ANTICORIT VCI products are an efficient alternative for and supplement to conventional temporary corrosion preventives, especially during transportation and storage. VCI products are effective in the vapor phase, i.e. they release their active substances into the atmosphere of a packaging until it is saturated, thus effectively protecting metal surfaces against corrosion. Such products are available as papers and foils for various packaging tasks, as powder, bag or pellet for insertion and as VCI oils for the internal preservation of closed systems, such as hydraulic systems or gearboxes.