Corrosion

This is another rather anodyne, technical blog which may disappoint those expecting witty (?) tales of derring-do. So, you have been warned!

Long time yacht owners will be aware of the corrosion issues at the junction of dissimilar metals. They will be conscious of the need to treat stainless steel screws used on an aluminium mast with an anti-corrosive joining compound like Duralac, or they will have struggled to remove corroded screws, seemingly fused in place.

They will be aware that the yacht needs to have anodes on the hull, propeller and other immersed metal parts and that these anodes erode and need replacing.

They may also have heard stories about rogue voltages causing havoc on pontoons and people finding that their propeller has disappeared while they have been away and connected to shore power…

Advice on the subject seems to be contradictory, subjective and a result of second-hand experience and anecdote. One would be forgiven for thinking that there are dark forces at play, and it is for this reason that I fitted a galvanic isolator on my shore power supply.

It was difficult to find anyone to say that it was the answer but, then again, no-one would say that it was complete bollocks – rather like my ultrasonic anti fouling system which pings away continuously…

So, with Hejira having been off limits due to Covid restrictions in the humid, salty environment of the marina in Nice, and with the windlass not having been used since September 2019, it was not surprising that there might be some residual issues. The extent of the corrosion however, which appears to be terminal, was surprising and disappointing as I had only replaced the windlass 10 years previously.

So, in removing the windlass for assessment, it became clear that it is really beyond repair. Although the ‘internals’ are okay, the casing is completely buggered by corrosion so it is more cost effective (apparently) to just replace the whole unit.

I considered cheaper versions but they would inevitably have required different fixing and aperture holes so I decided to replace ‘like for like’ – again! I was reminded of an experience anchored off Lundy Island in the Bristol Chanel some years ago when the windlass breaker repeatedly tripped and I ended up rigging the electric halyard winch to help weigh the anchor. This has convinced me to specify the supplementary manual over-ride arrangement, just in case. I also discovered, when removing the corroded windlass that there were two wires unused and realised that these were for a chain ‘counter’ to measure the length of chain deployed. I had previously marked the 100 metres of chain with a painted formula on the links which would indicate the length of chain as it descended. Over the years, the paint had become difficult to identify and decipher and I was intending to repaint the chain before the forthcoming season. It occurred to me that a chain counter would be a good enhancement. How much better to just give an instruction in the cockpit, ‘put down x metres’, before the crew go forward to drop the anchor. So a chain counter was also added to the shopping list.

As I write I am awaiting delivery of the replacement windlass and gear which is, apparently, on a long delivery as it is being made to order by Lewmar, the manufacturers. So there may be an equally boring subsequent blog covering it’s installation, commissioning  and first use…

So, by way of conclusion, the lesson learned is to always ‘run’ the various systems and equipment to keep it all functioning and to be aware of potential  electrolytic situations, however obscure, which might promote corrosion. This is especially pertinent where dissimilar metals are involved. In future, my anchor chain will not stow on the windlass gypsy and the windlass will be inspected and ‘worked’ regularly, It will also be liberally and frequently sprayed with the ubiquitous, WD40.