Within the corrosion resistant coatings market there is an increasing trend for zinc-nickel coatings. This trend can be explained due to prolonged warranty periods as well as increasing quality expectations. Zinc-nickel has many advantages when compared to zinc and or other zinc-alloys.
With one of the key features of course being the superior corrosion resistance even after mechanical damage and/or exposure at elevated temperatures. ZINCROLYTE Sprint offers all the advantages of this coating, coupled with a faster plating speed.
Figure 1: Demonstrates the corrosion performance of zinc-nickel plated fasteners (14%nickel) compared to zinc. When tested according to ISO 9227.
ZINCROLYTE Sprint is an advanced alkaline zinc-nickel process that is engineered to consistently deliver high speed plating rates, especially in bulk operation on complex parts commonly used in automotive and other high value applications.
The corrosion resistance of the zinc-nickel coating is exceptional, providing unrivaled protection for steel substrates. MacDermid Enthone’s passivates (TriPass ELV) and sealants/ final finishes (ENSEAL/TNT) are applied to further enhance optical appearance (black/shiny silver) or to meet pre-specified coefficient of friction values.
The ZINCROLYTE Sprint process deposits 12-15% -wt. of nickel (γ-phase zinc-nickel) and meets the most demanding automotive industry corrosion protection requirements.
The process exhibits exceptional throwing power while imparting smooth and uniform deposits with very homogenous alloy composition in both high- (HCD) and low current density areas (LCD).
Enhanced Plating Speed
The ZINCROLYTE Sprint process features high plating speed that is maintained over the entire bath life, with an enhanced current load capacity to deliver significant faster plating speeds than conventional alkaline zinc-nickel processes.
The new additive systems allow this to maintain its high performance without any auxiliary equipment
Figure 2: Shows an example when parts are treated under identical operating conditions, looking at; thickness, distribution
and uniform Ni incorporation.
Conclusion:
The ZINCROLYTE Sprint provides higher performance which permits considerably less plating time than conventional alkaline zinc-nickel processes.
Even and Smooth Appearance
Conventional alkaline zinc-nickel produces parts with good brightness, exhibiting globular nodules on the surface, which can be seen in electron microscope (SEM) micrographs. Special care is often required to keep these nodules tightly spaced and therefore ensure smooth surfaces.
ZINCROLYTE Sprint naturally produces a more even and smooth surface resulting in a brighter finish.
Figure 3: ZINCROLYTE Sprint surface characteristics, beautiful uniform silver like finish.
Furthermore, this enables a brighter finish to be obtained which facilitates improved passivate receptivity and enables a narrow range of coefficient of friction control.
Figure 4: ZINCROLYTE Sprint and conventional alkaline zinc-nickel surface characteristics compared
Highest Efficiency
ZINCROLYTE Sprint maintains a > 30% faster plating rate versus a conventional zinc-nickel process. This high current efficiency is consistently maintained over the entire bath working life.
Figure 5: Compares the efficiency of ZINCROLYTE Sprint versus conventional alkaline zinc-nickel run at 1 A/dm2.
Robust Operating Window & Reduced Maintenance
ZINCROLYTE Sprint requires less maintenance than conventional processes as it does not require any freezing such as carbonate crystallization and does not create any scales on anodes or other equipment. Furthermore, higher conductivity results in reduced cooling.
ZINCROLYTE Sprint offers good burning resistance, while consistently imparting smooth and uniform deposits in both high and low current density areas. This results in faster plating of complex part geometries.
Figure 6: ZINCROLYTE Sprint demonstrates consistent high efficiency even with increasing salt concentration versus conventional alkaline zinc-nickel.
Summary
Compared to conventional alkaline zinc-nickel the ZINCROLYTE Sprint has several advantages.
*No additional bleed and feed required in barrel application. Standard drag-out will normally suffice.
Figure 7: Compares ZINCROLYTE SPRINT features against conventional process.
It is important to note that the plating line equipment needs to be able to handle this more efficient process. When installing ZINCROLYTE Sprint, rectifiers or system control must be assessed to ensure the plant can handle the extra capacity.
ZINCROLYTE Sprint is specialized to generate revenue at high plant utilization.
•High plating rates – even after high throughput,
•High conductivity – lower bath voltage,
•Excellent metal distribution – uniform appearance,
•Higher burning resistance – can be run at higher current,
•No sludge in tanks or pipes, no scales on the anodes,
•No freezing out of salts necessary. Less maintenance.
Higher productivity = high efficiency + high applicable currents (enhanced burning resistance). Productivity achieved without the use of special equipment.
Mehmet Eren
Technical Sales Engineer
MacDermid Enthone Industrial Solutions
