The demand for corrosion protection continues to grow among many industries. Zinc is a common metal for guarding against this issue. More recently, the use of zinc alloys has produced significant results in improving the capabilities of zinc to provide this extra level of security against such destructive forces. In particular, zinc nickel electroplating is the choice of many industrial concerns to meet this need in spite of the extra cost the addition of nickel causes.
The Basic Process
Using zinc-nickel requires a comprehensive understanding of the two metals and the processes involved. Electroplating requires the use of a bath – either:
1. Alkaline – provides superior distribution of the zinc-nickel alloy over the component
2. Acidic (weak) –challenging for wastewater disposal
In general, the preference is to use an alkaline bath.
ASTM Specifications
In Europe, RoHS compliance is important. In the United States, the focus is on ASTM specifications. These provide specific directions for achieving the acceptable type of zinc nickel electroplating for several different industrial components. The directives classify the zin nickel coating into both classes and types. The focus is often on Class 1 that divides the specific chromate conversion coatings into the following five types:
* Type A: colorless
* Type B: yellow iridescent
* Type C: bronze
* Type D: black chromate
* Type E: any colors mentioned above as well as an organic topcoat.
The specifications also note the pre-process of the component required before plating. The finish acceptable, the characteristics of the final product as well as the bath options listed previously.
Zinc Nickel Electroplating
Zinc nickel electroplating is a specific coating with one intent: to improve the ability of the products it coats to withstand the corrosive forces of a harsh environment. It protects parts of brass, cast, and malleable iron, copper, and steel. By adhering to the ASTM specifications, this sacrificial metal alloy works with the base metal to improve its longevity, durability and overall anti-corrosive properties.
