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Tips, advice and updates from the team at marinechandlery.com |

* TOP TIPS TUESDAY *

90. STAINLESS DOESN'T  RUST (OR DOES IT?)
Crevice corrosion_01

We all take our stainless steel fittings for granted, after all stainless doesn’t rust or does it? Stainless steel, as you probably know, was ‘discovered’ like all great things in the world in Great Britain by Harry Brearly and yes I have been known to rant on about the Hovercraft, the Harrier Jump Jet etc etc.

However let’s get back to stainless. Keel bolts, for example when buried in timber are in a non-oxygenated environment and thus the corrosion resistance can be adversely affected likewise the fastenings used to bolt a pintle(s) or gudgeon(s) to a wooden rudder.

Crevice corrosion_02
Crevice corrosion_03

Now to get a bit more technical:

Crevice corrosion is a localised form of attack which is initiated by the extremely low availability of oxygen in a crevice. It is only likely to be a problem in stagnant solutions where a build-up of chlorides can occur. The severity of crevice corrosion is very dependent on the geometry of the crevice; the narrower (around 25 micro-metres) and deeper the crevice, the more severe the corrosion. Crevices typically occur between nuts and washers or around the thread of a screw or the shank of a bolt. Is this the reason the anchor swivel failed?

Crevice corrosion_04

Crevices can also occur in welds which fail to penetrate and under deposits on the steel surface. 

Now here’s an interesting one, self assembly rigging terminals from manufacturers such as Sta-Lok or Petersens. At Sta-Lok they used to write (nowadays its personal preference) that for ‘interior waterproofing, you should unscrew the two parts and insert a blob of silicon rubber about the size of a grape on the former inside the bottom of the end fitting before assembling, Petersens don’t believe in filling the fitting with silicon, they reccomend regular flushing with fresh water.

Our recommendation is that at this time of year, go over all your stainless steel shackles, swivels, rigging screws etc with a fine tooth comb and check their integrity, if the mast is down likewise all mast fittings. If the mast is still up and assuming the wind abates before it gets too cold up you go in a bosuns chair and check out all the stainless fittings.

If you want to bring your stainless back up to a ‘new look’ there are a number of excellent polishes on the market. Vistal works well and can be used with success on a number of other substrates. Shurhold Magic Wool is an excellent product for a wide variety of surfaces and of course there is the excellent Daveyshine high performance metal polish. If abroad where temperatures are in general warmer, Spotless Stainless is my favourite. Why? Because there is no work involved! Paint it on, (suggest you crack open a can at this stage) leave and as long as its not allowed to dry out  your stainless will look like new in no time!

Spotless Stainless_01
Spotless Stainless_02
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