The Dreaded Zinc Whisker

Careless Whisker !

Here at RMS we are finding an ever increasing demand from Contractors, Specifiers and end users for information regarding the potential harm caused by the possible growth of 'Zinc Whiskers'.

In our market place there seems to a large amount of contradictory information regarding the extent or the actual potential problem.

With over 10 years experience as a UK Distributor and more recently as a manufacturer of supplying Cable Basket, one commonly perceived possible cause of zinc whiskers in its standard form with BZP coating, we have decided to enter into the zinc whiskers debate to try and dispel some myths surrounding this issue.

Having supplied both the Electrical Contracting and Data Installation industry on several major UK contracts over the last 10 years we have yet to have a reported instance of the build up of zinc whiskers on BZP Cable Basket brought to our attention. Also we have had no reported problems with any of our zinc rich galvanised containment products supplied in conjunction with BZP finish Cable Basket during this period.

We are not doubting that there is a possibility that zinc whiskers could be found in samples of dust collected and tested from a typical Data Centre Installation but the source of the whiskers could originate from any BZP coated material including the massive amounts of common fixings used in the installation of material.

One advertising article pinpoints the problem to the build up of zinc whiskers on the underside of the floor tiles in the data halls, it is common to find these coated on the underside with a flat sheet of metal which can be either pre-galvanised or BZP plated.

The fact that the article doesn't point out that the very pedestals the floor tiles are mounted on; and the grills in the air handling tiles can also be of the same material and therefore logically pose the same level of risk is a little odd.

Having read a vast number of the postings and articles on the Internet the zinc whisker debate seems to be being fuelled by companies offering deep cleaning services for Data Centre Installations. Some of this information does seem to use a scare mongering approach which does tend to cloud the facts somewhat.

When we researched recent projects where we have won the contract to supply containment products and those we have lost, it is clear that in many cases the coating material that ends up being supplied or approved is indeed varied to say the least.

We know of data installations where a very wide range of coatings on Cable Basket in particular have been supplied with no discernible problems as yet.

These include standard BZP, Hot Dipped Galvanised, Zinc Passivated, Powder Coated, Stainless Steel. and even pre-galvanised.

Our competitors don't seem to be keen to come out and make a clear positive statement on the subject, often letting the customer or specifier make the choice even if it challenges material or coatings supplied on similar projects.

We have also canvassed the opinions of the manufacturers of the data cabinets and associated air handling systems to try to and get a detailed understanding on the performance of the filters used.

The common consensus would lead you to believe that the zinc whisker problem is not a commonly experienced problem, due to the high standard of particle filteration now recommended.

At RMS we offer a large range of product coatings to combat the problem, below we have listed our own opinions as to suitability for Data Centre Installations. We must stress that they are just our opinions.

BZP Bright Zinc Plate

This is the most commonly supplied coating in the Cable Basket industry, it has been in use for many years. We have supplied this material in both the outer areas of Data Halls and indeed the Data Halls themselves with no reported problems

This coating is used on most fixings used to install material and in many cases the floor tile pedestals are BZP Coated.

Hot Dipped Post Galvanised After Manufacture

This coating applied over bare material after manufacture is commonly used on external installations to prevent corrosion. Once again we have supplied it in Data Halls where it has been asked for as a means on insuring there are no zinc whiskers. The process of Hot Dipped Galvanising tends to leave excess flakes of coating that will fall off during installation and handling of the product. However it is very stable after any residue falls off during installation.

CPC Coating

RMS currently manufacture a Cable Basket in bare wire which then has a clear epoxy resin applied over it. The resin has a performance level that rivals post galvanising in the prevention of corrosion but none of the draw backs. Its smooth finish prevents any damage to cables during installation. When cutting the material the touching up of the cut wire is easily achieved with a low pressure aerosol application. We can attach a earth tag to the basket lengths to maintain earth continuity of the product.

The durability of the resin is easily measured as it was applied to the external cable tray installed on the roof of the Bluewater Shopping Centre nearly 14 years ago. It was also applied to all of our containment installed in the new Terminal 5 Car Park so as to prevent the pre-galvanised trunking and cable tray dulling with age, such was its success that we coated many other unrelated products on this site.

We will gladly offer samples of the material for appraisal

Nickel Coating

We are currently able to offer this as a potential zinc whisker solution, there is a cost factor involved in the coating process due to higher price of nickel. in appearance it is hard to tell Nickel and BZP apart. We understand that some manufacturers of floor pedestals are experimenting with coating this to overcome the perceived zinc whisker issue.

We are not sure that the cost equates to the benefits but it is possible that it is a solution. If its use becomes common I am confident there will no doubt follow a huge mass of Nickel Whiskers articles written by various cleaning companies.

Coloured Powder Coating

Again at RMS we have supplied projects with material powder coated in several colours which removes the zinc whisker risk and has the added advantage of offering clear and easy identification of cable runs. The drawback using this material finish is the potential visual damage to the coloured finish with all of the handling during the installation process. Unprotected bare metal beneath the coating if not treated will eventually corrode leaving other issues to be dealt with.

Pre- Galvanised

Whilst we can offer our Cable Baskets manufactured from pre-galvanised we do not see any benefit using the product. The product is usually only offered by those companies not actually manufacturing their own mesh.

The process of welding a typical 300mm wide 60mm high Cable Basket means there are upwards of 300 spot welds on a length. The heat and energy needed to weld two large diameter wires means that the galvanised coating can be burnt off during the process. The process itself leaves black marks on each weld that for a period of time disguises the lack of galvanised covering on the weld. it can be argued that a sacrificial coating of galvanising is left behind during the welding process but it is evident from samples we have left exposed that oxidization occurs very quickly and rust can and will follow. The potential of white residue from oxidization on 300 individual welds and the possibility of actual rust can pose as big a problem as zinc whiskers

Stainless Steel

This product will obviously alleviate the zinc whisker issue but its cost can be prohibitive. Obviously the potential damage to circuitry in a Data Hall could cost many thousands of pounds so it could be argued that the cost becomes irrelevant. We have only known of a few installations where the specifying engineers have for ultimate peace of mind specified this material.

Our conclusion at RMS in all of this is there is definite for further and prolonged investigation into containment and fixing products supplied and fitted into the sensitive Data Hall area. We are continuing that investigation and invite specifying bodies, clients and contractors alike to further discuss this issue and help the industry to have a clear definitive answer if it can be found. The rise of link driven advertising of cleaning companies we don't think is helping the matter.

We will continue to offer all of the solutions above except pre-galvanised cable basket because of the damage caused in the welding process as stated above

We will of course be prepared to offer any other alternatives if suggestions are forthcoming.

The reason for writing this blog is not to put our head over the metaphorical parapite or a cheap advertising stunt it is purely to stimulate discussion which we hope will enable us to have a confident answer.

Marc Swaffer Director of RMS Ltd