Published: 11 June 2012
Category: Technical articles
Electrolytic action will result in corrosion at earthing and bonding connections
Severe corrosion may be found only a few weeks after an aluminium label has been installed in contact with a clamp strap and a copper pipe.
The label must be removed from the strap before attaching the clamp to the pipe.
The slots in the labels are intended only as an aid to packaging and storage. The label should be screwed to the clamp using the round hole. Alternatively, the insulated protective conductor should be threaded through the round hole in the label in such a way that there is no contact between the label and other metals. Where a protective conductor is too large to pass through the holes, the label can still be attached to the protective conductor by using some smaller diameter insulated wire or insulated cable tie.
Solution
The aluminium warning label reading "Safety Electrical Earth - Do Not Remove" supplied with an earthing or bonding clamp to BS 951 must not be installed in contact with a dissimilar metal (Regulation 522.5.2 refers). This is to avoid corrosion due to electrolytic action. Electrolytic action is a common problem with aluminium.The label must be removed from the strap before attaching the clamp to the pipe.
The slots in the labels are intended only as an aid to packaging and storage. The label should be screwed to the clamp using the round hole. Alternatively, the insulated protective conductor should be threaded through the round hole in the label in such a way that there is no contact between the label and other metals. Where a protective conductor is too large to pass through the holes, the label can still be attached to the protective conductor by using some smaller diameter insulated wire or insulated cable tie.