Zinc: Trivalent vs Hexavalent

 

 

Zinc Plating is a very popular process for the protection of a wide range of components. It’s a sacrificial coating that offers excellent corrosion resistance at a cost effective price. Zinc Plating is also known as galvanising and can be passivated in a number of colours. The way in which Silchrome carry out our Zinc Plating process has been updated, and we are now offering Zinc Plating that uses Trivalent Chrome rather than Hexavalent.

 

Why The Change?

 

Hexavalent Chrome (chrome VI) is a known carcinogen, meaning that it’s bad for the environment and for our staff carrying out the process. On the 21^st September 2017, Hexavalent Chrome will be subject to increased restrictions after being placed on the European Chemicals Agency’s Annex list for some time. Hexavalent Chrome is an element in processes including Zinc Plating. As such leading chemical manufacturers have sought to find a way to replace hexavalent chrome whilst obtaining the same levels of protection.

 

Production Changes

 

The small switch to Trivalent Chromium has big impacts on production. Zinc Plating using Trivalent Chromium has a higher efficiency with more uniform distribution. It’s also possible to Barrel Plate with Trivalent. This means where you have a larger volume of smaller parts that need Zinc Plating, this process can be carried out more cost effectively.

 

Colour Variation

 

Most people who are familiar with Zinc, will be used to the range of different coloured passivates which are used in the process. These include: Blue, Yellow, Black and Olive Drab. In the past the yellow colour was actually created through the use of the hexavalent solution and the ‘stronger’ the colour, the more hexavalent chromium that was used. Now, with new Trivalent Chrome the colours that are produced are actually a ‘weaker’ colour in tone, but this is not connected to the performance of the coating. In many cases a dye will now be used to create a desired colour. As such you would expect that Zinc and Clear will now have a light iridescent blue colour to it.

 

Advantages

 

As with any other process, Silchrome are always keen to test the expected results. As such we have independently tested the quality of our Zinc Plating which incorporates Trivalent Chromium, and have seen it perform up to 1500 hours under ASTM salt Spray Tests. We would expect the performance of Trivalent based plating to match that of its predecessor.

 

What Silchrome Offer

 

We are currently phasing out our use of Hexavalent Chrome within our Zinc Plating offering in order to comply with REACH protocol. We are still offering both processes for those customers who require Hexavalent, but longer term we expect all of our Zinc Plating will be Trivalent based. We are an ISO 9001 and ISO 14001 certified plater based in Leeds, West Yorkshire and are happy to answer any questions you might have about plating.