Zinc plating is the process of electrodepositing Zinc onto Mild Steel or Iron parts. The main benefits of Zinc Plating are that it offers excellent corrosion resistance as it is a sacrificial coating in that the zinc coating slowly corrodes over time protecting the steel/iron part underneath. The other main benefit is that the coating itself improves the look of the base metal as clear zinc plating has a bright silver/blue appearance.
For better corrosion resistance the zinc layer is passivated we offer 3 types of passivation and 1 topcoat as follows:
Clear (blue) passivate (trivalent chromium)
Mainly used for machine parts and washers, screws, fasteners, good for decorative purposes as it can be finished to a bright shiny silver/blue finish.
We also offer a topcoat seal that is clear so can be applied on top of any of our passivates. It typically increases salt spray resistance by 150 hours.
Yellow passivate (trivalent chromium)
Yellow passivate offers a better corrosion resistance and is more often used for motor parts and general parts to be used outdoors.
Black Passivate (Trivalent Chromium)
Black Passivate offers excellent corrosion resistance and is mainly used for decorative purposes where a dark finish is required.
What Thickness do I require?
1 – Mild Conditions (Indoor use/mild abrasion) = 5um
2 – Moderate Conditions (Indoor/Occasional Condensation / abrasion = 8um
3 – Severe Conditions (Outdoor Infrequent Rain / Cleaners) = 12um
4 – Very Severe Conditions (Harsh environment / high abrasion) = 25um
An approximate guide to service life, mean corrosion rates (Zinc only not including passivates or topcoat);
1 = <0.5um/year
2 = 0.8um/year
3 = 1.2/1.5um/year
4 = 5.6um/year
The most common material substrates for zinc are carbon steel, unalloyed steel, low alloyed steel and cast iron.
By applying a heat treatment after zinc plating hardened steels can also be zinc plated. The heat treatment is necessary to avoid hydrogen embrittlement.
To get the best results for zinc plating the condition of the material is very important. Clean rust/scale free metal allows for the most cost effective best finish. Hot rolled steel requires heavy pickling and as such is a more expensive process. With used motor parts to ensure the best finish these parts should be bead blasted before zinc plating to ensure the surface is of the best condition and is free of any paint.
Note: The above information should be taken as a guide and not fact.