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Passivations are processes that make electrolytically deposited metal surfaces have a greater corrosion resistance through protective coatings on the basis of CR III through a non-electrolytic immersion chemical process.
This protective layer of inorganic nature provides a passivation of thickness in manometric values, which is why it does not interfere in the tolerance deviations of the workpiece and is totally free of Cr VI.
The various passivation methods vary based on the protection against corrosion and the required visual and aesthetic aspect.
Passivations are improved often by adding a Sealant and Top Coat.
These final layers of an organic nature mineral ensure not only greater protection against corrosion, but also a more consistent appearance of the surface.
There are different types of passivations for each type of finish, all of them free of Cr VI:
- Transparent passivations for Zn and Zn/Ni finishes
- Bluish passivations for Zn and Zn/Ni finishes
- Passivations of a thick layer of iridescent appearance for Zn finishes, with better corrosion protection than transparent or bluish ones, providing a thicker layer of film (200 – 500 nm)
- Intense black passivations both in Zn and Zn/Ni finishes
These passivation layers also provide improved adhesion and adherence properties regarding the metal of the electrolytic coating that are suitable for any type of finish, either powder paint, kataphoresis, organic and lamellar coatings, application of rubber, etc.
We offer a range of passivations, from highly aesthetic finishes with less corrosion resistance to the most advanced ones with a thick layer that exceed 480 h to corrosion without additional seals, with the advantages that this implies for the elimination of drop seal or adherence in the subsequent application of organic or rubber finishes.
Some of these passivations have exceptional thermal white corrosion resistance features, even after they have been dehydrogenated on the passivation, so they are suitable for engine compartment components subject to high temperatures.
These same passivations maintain the properties of coatings such as Zn/Ni on which they are applied and are not affected by corrosion in contact with aluminium, which is an increasingly common aspect in the new projects of the automotive industry.
We also have new passivations free of Co that are respectful with the environment, meeting the new standards established by the SVHC REACH regulation and that, in turn, provide the same degree of protection against corrosion than its counterparts with Co without its negative environmental impact.
This passivation offers the highest level of protection to corrosion (above 1000 h) and is resistant to temperature up to 12 h at 210º C, with possible subsequent dehydrogenation.
In addition to these passivations, it is possible to apply Sealants and Top Coats as final layers that provide an organic mineral character free of Cr VI and that guarantee a greater protection against corrosion, which in some cases could reach up to 2000 hours of protection from red salts.
These Sealants and Top Coats give the passivation a uniform clear look and considerably increase its resistance to temperature without changing the features of corrosion.
They give the finish extra resistance to abrasion, scratching and mechanical stresses without altering its anti-corrosive properties.
The Sealants and Top Coats may be applied with or without lubricant for the adjustment of the coefficient of friction, being integrated into the product itself and allowing to parameterise the standards of automotive manufacturers, obtaining values of 0.06 to > 0.18 in assemblies with steel, thus covering the whole of the specifications requested by the different manufacturers.
All of these lubricants are specified and requested in different standards; some of them are: Torque ́n Tension 15, Torque ́n Tension Control Fluid, Gleitmo, Gardolube. Corrosil Plus 415, etc.
According to demand these Sealants and Top Coats contain an additive visible under Ultraviolet light to control of the correct application of the coating.
The passivations based on compounds with Cr (III), and all of our Sealants and Top Coats meet the legal standards set by the EU RoHS Directive as well as by Directive 2000/53 End of Life Vehicles.