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STAINLESS STEEL CABLE CLEATS – PREVENTING GALVANIC CORROSION OF CABLE FIXINGS

In the following article we provide an evidence based specification case for stainless steel cable cleats where levels of atmospheric corrosion preclude use of other cable fixing materials.

One of the most important issues to consider when specifying cable cleats is the risk of material corrosion – not just as a result of the installation environment, but also from other metals which the cable cleat is in contact with.

Galvanic corrosion occurs when dissimilar metals are placed in contact with each other in the presence of an electrolyte. There are two factors that affect the rate of galvanic corrosion, the first is the distance between the two metals in the galvanic series.

The further apart the two metals are in the galvanic series, the greater the risk of galvanic corrosion – with the metal higher up the list (more anodic) being the one whose rate of corrosion is accelerated.

The second factor to consider is the relative surface areas of the different metals.

If the more anodic (higher up the list) metal has a smaller surface area than the metal it is in contact with, the difference in surface area causes the rate of corrosion of the anodic metal to increase.

Conversely, if the more anodic metal has a much larger surface area than the cathodic metal, it may be sufficient for the effects of galvanic corrosion to be discounted. In terms of cable cleat selection, the surface area of the cleat is generally significantly smaller than the structure it is mounted on.

Therefore, if it is made from a metal that is more anodic than its support structure it will be susceptible to galvanic corrosion.

Conversely, if the cable cleat is more cathodic than its support structure, there is little risk of galvanic corrosion.

Using this criteria, if galvanised ladder is the support structure, and there are no other significant factors, it is safe to use ball lock stainless steel cable tie. However, if the support structure is stainless steel, separation should be provided if aluminium or galvanised cleats are used.

Galvanic corrosion is not easily predictable and can be influenced by the type of electrolytes present such as salt water or fresh water containing impurities. In general terms when guarding against galvanic corrosion, the safest course of action is to separate dissimilar metals with polymer separation washers.