While servicing moorings in the Russell area we have identified a ‘high electrolysis activity zone’ in the northern end of the Russell mooring area.

Environmentally occurring electrolysis zones are known to occur in random locations along the Northland coast. There are also areas where human induced electrolysis occurs in varying degrees.

The jury is out as to whether the increased level of electrolysis is environmental or human induced – it may be a combination of both. The current levels of electrolysis are causing accelerated wastage to mooring components – particularly top chain and shackles.

In recent months four moorings have failed due to accelerated steel wastage caused through electrolysis and corrosion. In the last year there have been over eight mooring failures due to electrolysis.

To identify whether there has been an ongoing issue with electrolysis in this area we discussed the issue with the Maritime Section of the Northland Regional Council including one of their staff who previously worked with the Harbour Board. He recalls high base levels of electrolysis in the bay which suggests that it’s presence isn’t recent, but its affects appears to have increased .

What you can do?

Given the increased levels of electrolysis and recent history of mooring failures, it would appear that the three yearly service regime is too long for this particular location. After discussions with the NRC we recommend that all mooring owners consider adopting a two yearly service regime for their mooring as a precautionary approach to protecting your boat.

What Moorings Northland is doing?

Given the implications of these issues, Moorings Northland has changed it’s work practices to protect your asset and our reputation by:-

· Using 20mm certified chain, instead of the minimum 16mm certified chain. Using the larger chain provides greater mass and thus safer margins against wastage.

· Using 26mm shackles instead of the minimum 22 mm shackles. One of our findings revealed that the smaller shackles failed. Particularly shackles that were only ‘tack welded’.

· Fully welding the pin on all shackles with an ‘electrically natural’ electrode. Moorings Northland never ‘tack welds’ as this form of securing shackles is known to fail.

If you have any queries or would like to alter your service regime to two yearly please contact us on 09 4026939 or email mooringsnorthland@xtra.co.nz and we will alter our records accordingly.