Neeves
Well-Known Member
This corrosion can be 'managed' - grit blasting and or acid washing will remove the rust and the surface will look almost as good as new. There is no flaking of pieces of rust - it seems to be superficial (but its just a picture and the corrosion might be more serious than illustrated).The photographs illustrate the problem with Spade anchors:
View attachment 182672
A look around a marina shows most of them are like that, seems to be regardless of level of use. Nor are they simple to refurbish.
A Spade anchor produced by someone else would be good - maybe the Scots who make such a good job of the Knox.
.
.
Galvanising works on clean steel - no rust, no paint. Even a grit blasted steel piece left overnight (during which it will continue to corrode, rust) will not galvanise well. The steel needs to be clean, grit or acid, and immediately galvanised.
The problem is that the Spade shank is hollow and its impossible to see the state of corrosion inside the shank (and the shank is a pretty critical component). The interior corrosion might be superficial - but galvanising will not 'work' on an unclean surface. You could pickle, acid wash, but too much acid will attack the steel and the welds - and even if you acid wash you have no idea how successful might be the practice.
So the interior of the shank cannot be galvanised - it will continue to rust.
From memory the amount of steel used to make a Spade shank is not much different to make an Excel, Rocna etc etc shank. I'd take a high tensile strength piece of steel, like Bis 80 (800 Mpa) and make a new shank from a piece of plate based on a plate thickness of twice the wall thickness of the anchor in question. I'd make it exactly the same profile, but beef up the tongue of the tongue and groove to fit the joint. The shank will then be, effectively the same weight as the old one (so balance the same) but will undoubtedly be stronger. I'd then galvanise the new shank.
Small Spades, upto I think the S80, have simple shanks, not the hollow shanks of the largest models. My idea is hardly novel.
On reflection - the issue is either fashionable or becoming of increasing frequency. I'd do this of any Spade with corrosion as illustrated - I'd not waste my time, money, trying to save the original shank.
You could do this at home - if you can source the steel. All you need is an angle grinder, the thin blades used to cut stainless, some abrasive discs to smooth out the curve + patience and time. When you have the correct shape you will need the joint beefed up (you will need to cut out the 2 needed pieces - and the have them welded). Make the new shank slightly over size at the joint and grind it down to a good fit (remembering the new shank will be slightly bigger (200 microns of gal) Finally you will need to abrade down to bare metal. You might think you need to profile the shank, make it knife like (as per the original) - research suggests this is 'nice' (as in pretty) but technical unnecessary. Just 'buff' the edges, round them off - to accept the galvanising. And round/buff the shackle slot. Then galvanise. Try to abrade back the day before you have it galvanised and oil as soon as you finish abrading, store in a sealed poly bag.
Nice, Pretty - Excel, Supreme work perfectly well with an un-machined shank - the machined shank looks nice, it looks like attention detail, it looks sensible - but a waste of time and money (tests have been done).
Jonathan



