Zinc Plating Black Passivation

Rohs compliant black finishes for zinc plating vary.

Zinc plating black passivation. 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. 3 zinc nickel black or grey passivation. I have a customer that calls out zinc passivate as the finish on their cold rolled steel 1018 steel on a small hat section bracket job. Black zinc specially hex black chromate is not a good corrosion resistant finish if not specified some topcoat sealer or lacquer.

The passivation on zinc gives an extra protection and determines its final colour. Zinc plating is a form of electrochemical galvanisation. Zinc provides sacrificial protection to a substrate such as iron or steel when the coating is incomplete or is damaged during assembly or service. Barrel plating is available in acid based zinc solution which is ideal for small items like bolts fixings perfect for cast material.

My experience with acid zinc plating and only hex black chromates isn t good as i haven t seen more than 12 hours for white rust in neutral salt spray chamber test astm b117 affil. In this case the first layer is an alloy of znfe. Others use formulations that are actually black plated. Most systems utilize a post treatment over the black passivate to give further corrosion resistance.

Zinc plating is available on components made of steel copper or brass in vat or barrel version. The passivate works well over acid chloride zinc both ammoniated and non ammoniated systems cyanide zinc alkaline cyanide free zinc and zinc iron cobalt alloy deposits. Black passivation 48 hours. Link to spec at techstreet.

This protection is vital in some circumstances. Afterward a black or grey passivation can be achieved on the surface. Chromated zinc is sometimes used as an undercoat for paint. Black passivate offers excellent corrosion.

2 zinc iron plating black or grey passivation. Olive drab and call it black zinc. Coldip midnight 1500 is an easy to use trivalent black process with a simple three part system which allows for maximum color control and provides a consistent black appearance. The black oxide finish requires a post treatment like an oil or wax which will not perform as well as a zinc plated part with a rohs black passivate.

Some suppliers use a black oxide coating or dye over the surface of zinc plating e g. What is zinc passivation 2002. The level of corrosion resistance of the latter will be somewhat lower than that of gold zinc but better than clear passivate. There are several systems on the market.

Usually the black passivation requires a further top coating usually organic coating by immersion to be more resistant. Glmf specializes in trivalent passivation for zinc and yellow zinc and clear zinc and black zinc and olive drab zinc nickel stainless steel passivation and other finishing processes to meet our customer s specifications.