PLATING WITH TRIVALENT CHROME PASSIVATION APPLICABLE ON FERROUS ALLOYS.
PROTECTION AGAINST CORROSION AND INCREASING OF HARDNESS WITH GOOD DUCTILITY.
trivalent chrome Passivation in according to the RoHS standard.
It produces a self-healing conversion layer.
It adds a hard, semi-glossy and resistant film to the materials.
The passivation layer is suitable for receiving subsequent sealants.
Exceptional corrosion resistance: over 900 hours in NSS with red salts without sealant
Zn-Ni alloy (zinc nickel), usually
composed of about 85% zinc and 15% nickel, are coated on carbon steel
as a protective coating in a process similar to the way they are applied
Zn-Ni coatings typically consist of a layer ranging from
8 to 14 μm followed by a trivalent passivated layer between 0.06 and 0.15 μm
and a sealing layer from 0.5 to 4, 0 μm.
The zinc nickel plating significantly exceeds the protection offered by other coatings in three main aspects:
• It offers greater protection against corrosion
• It provides greater resistance to wear in moving parts
• It limits thermal stress to parts subjected to higher operating temperatures.
In the galvanizing process, zinc nickel coatings also have a good penetrating
power in complex geometries and particular cavities.
Corrosion protection: Zn-Ni coatings are designed to provide anti-corrosive protection two to three times more than zinc coatings.
Furthermore, the crystal structures of the Zn-Ni deposits are
a single uniform structure that creates a thin and uniform protective layer over the
entire coated surface. The aluminum parts have become more widespread for automotive components.
Due to the high potential of aluminum in contact with steel, aluminum
parts are subject to galvanic corrosion attacks. Fortunately, accelerated corrosion
tests show that the nickel zinc coating also protects against this type of
phenomenon often called “stack effect”.
Hours spent before white and red corrosion compared between the two
coatings Increased wear resistance: a hard and thin Zn-Ni coating has a
uniform and smooth finish that increases wear resistance,reducing both friction and the possibility of abrasion.
On the Vickers hardness scale, the parts coated with Zn-Ni
also reach 450 Hv, compared to less than 150 for parts coated with zinc.
Resistance to thermal stress: zinc nickel coatings provide greater protection against thermal stresses. The tests show that the components coated with Zn-Ni maintain their resistance to corrosion, despite exposure to thermal stresses up to 300 ° C. The parts coated with zinc instead resist thermal stresses up to only 120 ° C and then lose corrosion resistance.
Zn-NiI zinc nickel coatings can provide a much higher degree of
substrate protection, which means that they can withstand the stresses
that inevitably shorten the life of the components, from equipment with
moving parts to buildings and infrastructure .
THere are some industries, including the automotive and aerospace industries, have already widely adopted these coatings. Others, such as constructors of construction, agriculture and power transmission equipment, are beginning to exploit them to
protect the value of their products. Agricultural and construction equipment is continuously exposed to time and often to corrosive fertilizers, herbicides and road chemicals.
Zn-Ni-treated carbon steel can also be used to replace more expensive materials used to resist corrosion. In many industries, machine builders have replaced it with
stainless steel to increase corrosion resistance. Carbon steel with
Zn-Ni coating can reduce component weight as well as control costs.