Spade corrosion

[BabaYaga]

This is my A80 aluminium Spade anchor, bought in 2003, on its bracket on the stern rail.
The crack, probably due to some corrosion between the aluminium and the internal lead ballast, has been evident for a few years now.
There is a similar crack, though less pronounced, on the other side of the fluke.
How concerned should I be? Any ideas on course of action?

 

[Bobc]

Not at all concerned IMHO. Fill it with some chemical metal if you don't want to look at the crack.

 

[noelex]

This has been a known problem with the aluminium Spade. It needs replacing.

If you contact Spade I would be surprised if they do not offer a replacement at no charge. Let us know the outcome.

 

[noelex]

Not at all concerned IMHO. Fill it with some chemical metal if you don't want to look at the crack.

The “crack” is caused by dissimilar metal corrosion between the lead ballast and the aluminium in the presence of seawater. The lead ballast does not expand with corrosion like steel so the “crack” strongly suggests there is considerable internal thinning and weakening of aluminium fluke.

This needs to fixed, not patched.

 

[vyv_cox]

The pits in the surface are also due to galvanic corrosion between lead and aluminium: there is a photo of a similar one on my website. It is always difficult to predict the effect of a crack but one as long as that should not be ignored. The one on my website was replaced FOC for the second time but they were only a couple of years old. Being much older, Spade may not be interested in yours. Must be worth a try though.

 

[BabaYaga]

Many thanks for the replies so far.
I will start by contacting the distributor here (same company that I bought from 16 years ago, a good start...).

 

[rszemeti]

I'm struggling now to see why anyone would want an aluminium anchor ... weaker than steel, but with lead ballast to bring it back to the same weight? When you combine that with the limited fatigue life of aluminium, it makes no sense to me why anyone would want one.

 

[vyv_cox]

I'm struggling now to see why anyone would want an aluminium anchor ... weaker than steel, but with lead ballast to bring it back to the same weight? When you combine that with the limited fatigue life of aluminium, it makes no sense to me why anyone would want one.

Thousands of us use Fortress anchors and only have good things to say about them, but I agree about adding lead ballast.

 

[prv]

The steel spades have lead in them too - it’s about weight distribution as well as overall weight.

Pete

 

[BabaYaga]

I'm struggling now to see why anyone would want an aluminium anchor ... weaker than steel, but with lead ballast to bring it back to the same weight? When you combine that with the limited fatigue life of aluminium, it makes no sense to me why anyone would want one.

The lead is there to put weight in to the tip, as a whole the aluminium version is still quite a lot lighter than the steel version – 7 kilos vs. 15 kilos for the size I am using.
Lightness is the only benefit, as far as I can see. For me this means ease of handling, as I tend to lift this anchor on stretched arms over the stern rail. On the bow I have a standard 16 kilo steel Delta – no major advantage of using aluminium there, in my view.
After 16 years with the aluminium Spade I am very impressed with its ability to set and with its holding power. The corrosion issue is certainly a disappointment, but for me it is the only one.
Limited fatigue life of aluminium... what about spars?

 

[Neeves]

Our alloy Spade (A80) is a bit younger than yours, 2006, and shows no signs of corrosion. My understanding is that after a few issues Spade added extra lead in the toe of the aluminium version and addressed the corrosion issues. I don't know what they did and hope our anchor has benefitted - but why spoil a good opportunity to knock Spade.

We also think the alloy Spade an excellent product, cannot tell the difference between it and the steel version (we have both and can compare) and the steel model sits at home (and has not been used for years).

We are an all alloy anchor wardrobe now. Aluminium Excel, aluminium Spade (both ballasted with lead) and Fortress (all roughly equivalent to their 15kg steel counterparts (we are a 38' cat 7t - and have the windage of a 45' AWB, specifically a 45' Bav)

Anchor performance is not about weight - its about design. I can quote any number of learned research papers that underline and confirm weight is simply not relevant - two identical anchor, one alloy one steel would perform similarly. Fortress is better than Danforth (though they are not identical - so its an unfair comparison), we cannot tell the difference between our steel Excel and alloy Excel and as mentioned cannot differentiate between the steel and alloy Spade.

If weight were important we would see ballasted oil rig anchors.

Anchor Right address the issue of corrosion between lead and aluminium by casting the lead in the toe and then isolating and sealing the lead from the environment by welding the pocket closed with an end plate.

On the strength of aluminium - the A380 is built effectively from aluminium. The Dreamliner is built from aluminium. Bombardier use aluminium

The shank of the aluminium Excel is engineered from the aluminium alloy 7075 which has a min tensile strength of 570 MPa. The shank is 18mm thick vs the shank of the steel version, using a 800 MPa, typical, steel, (which also sits at home) which is 12mm. The actual tensile strength of the 7075 alloy will be a bit higher than the minimum. Can anyone confirm the tensile strength of the shank of a Rocna? 7075 does not have the corrosion resistance of 5083 aluminium but our Excel has been sitting on our bow roller and sees regular use and shows no signs of corrosion. I have seen a number of rather brown looking steel anchors of many makes - some 2nd generation - but people eem to forget - steel corrodes. There are now more corrosion resistant higher tensile aluminium alloys (of which modern aircraft are now made) that can be formed and welded.

If corrosion is an issue for the base aluminium - there is a process, called anodising - which apparently is quite effective. Interestingly Guardian, the cheaper version of Fortress - is not anodised - and I have not heard of complaints of corrosion and the alloy used is, again. less corrosion resistant than 5083
There are many anecdotal stories put about by the internet armchair gurus about the disadvantage of aluminium anchors, forgetting that Spade may have addressed the issues, the aluminium Excel has been singularly successful in Australia, New Zealand, Canada and the NW USA, conveniently forgetting that many use Fortress and thee guru have not actually used an aluminium anchor themselves.

Sadly trolling does not require evidence.

As with any new design and concept there were teething problems with aluminium anchors, but there have been teething problem with steel anchors, bendy shanks for one (or two) and I can think of a number of steel model that were released - and sank like stones. I can list bad design features of modern steel anchors. Fortress have been around since the late 1980s - longer than any other second generation anchor, I don't know the lifespan of the alloy Spade but it has been around longer than most second gen anchor - and both are still on the market.

Look at aluminium alloys with a more open mind - you might be surprised.

Jonathan

 

[Neeves]

Baba,

If that is how you store your anchor - please change it!

The ballast chamber acts as a receptacle for water, rain or seawater. Your anchor possibly has exposed lead and aluminium with a pool of water on top - the perfect conditions for corrosion. I think Vyv will agree - corrosion needs water, better (I think) seawater. You are providing the perfect environment.

Jonathan

 

[BabaYaga]

Baba,

If that is how you store your anchor - please change it!

The ballast chamber acts as a receptacle for water, rain or seawater. Your anchor possibly has exposed lead and aluminium with a pool of water on top - the perfect conditions for corrosion. I think Vyv will agree - corrosion needs water, better (I think) seawater. You are providing the perfect environment.

Jonathan

Dear Jonathan, please tell me – how do I stop water from entering the ballast chamber when the anchor is deployed?

Seriously, stored like this the anchor will catch some (in my case, rain) water. I am fairly certain that when stored on a bow roller, in many cases (modern plumb bow, shank down into the anchor locker) the same will happen, only difference the water will be saltier.
If this results in corrosion and cracks, surely the cause is a design flaw rather than an operator error?

 

[Neeves]

I agree - to my uneducated eyes - a design error. That does not mean you could not cater for it. I'm not defending, in any way, this facet of Spade's design. I'm simply suggesting that if Spade come to the party (which I hope is the outcome (for you and them) or you buy another aluminium alloy Spade that you consider an alternative method of storage. I suspect your anchor does not spend THAT much time deployed - or put another way - I suspect your anchor is lashed as shown much longer than it spends in the water - the toe of your anchor shows minimal wear - mine, a mere sprog to yours is well worn

I'm not an expert on Lead/aluminium galvanic corrosion, at all. My understanding is water is needed and seawater, or dissolved salts, simply increase the speed of corrosion. Unless you wash your anchor each time you use it there will always be some salt present. It seems unnecessary and tempting fate to leave a pool of water where the 2 dissimilar metals co-exist. You would not, intentionally, leave your chain in a puddle of water, nor have a puddle of water surrounding your keel bolts (I hope) - why is an anchor special?

I don't know how often you have used your Spade but I can think of many 'design' or manufacturing faults on anchors that have become apparent much more quickly and affecting many more anchors than the few example from Spade. Your issue is not yacht threatening and has taken a long time to manifest itself - other 'errors' have been much more serious (or potentially serious) and impacted far more people.

No-one will thank me for listing them - most are very well known.

I'm hoping you bought your anchor from Bluewater Supplies.

But let us know how it pans out.

Jonathan

 

[Neeves]

Baba,

You have had 16 years of life from your aluminium Spade. I know you, and I, think it should last longer - Spade, or whoever, might take a different view.

I make the following suggestion if Spade are not too impressed with the idea of offering a replacement, or fail to make you an attractive proposition.

This depends on how handy you are and how much time you have.

I'd find a local fabricator skilled in handling and welding aluminium.

I'd make a plate to allow you to seal the ballast chamber. The seal does not want to retain too much air, as that will add buoyancy - so the plate needs to fit fairly snugly inside the chamber

I'd melt out the lead, keeping it all - so that you can weigh it and replace with the same weight. You might want to check the ballast weight, your empty fluke vs a current fluke with lead (I could weigh mine - but better a more recent model)

I'd examine the inside of the chamber and evaluate for corrosion. It looks as though the corrosion has 'simply' split the weld. if there is sufficient metal left to offer integrity I'd have the split weld replaced, this might mean cutting the panel off, grinding it down - or even replacing it. I'd then refill with lead and have the chamber sealed by welding on the end plate.

Now - someone else skilled in the art might say this is wrong - I frankly have no idea - if its a worst case scenario - it must be worth considering.

Jonathan

 

[noelex]

If this results in corrosion and cracks, surely the cause is a design flaw rather than an operator error?

I don’t think you will have much argument from Spade. This is well known defect with this model of anchor.

Spade UK offer a “lifetime warranty against breakage”. Your anchor sure looks broken to me.

The only difficulty you may encounter is that Spade sometimes require the defective anchor to be returned, and returned to a specific location. The transport costs especially if charged both ways can be considerable. Other companies such as Fortress and Mantus will normally accept photographic proof of the defect without the need to send anything back.

Incidentally, Spade USA offer a very generous warranty that covers just about anything including normal wear on the galvanising. Amazing.

Anyway let us know the response from Spade. Some anchor manufacturers are offering very generous guarantees that are more like an insurance policy rather than a normal guarantee. It is helpful to know, when selecting an anchor, how the guarantees from each manufacturer works in practice.

 

[Neeves]

his is well known defect with this model of anchor.

A bold statement, any numbers?

I know of a few oft quoted examples, 4 in total now. They don't get more by constant repetition.

I can think of hundreds of shanks that were either replaced or cause for replacement but have been quietly forgotten. I can think of a few bent toes - that don't even merit a question. Lots of regalvanised steel anchors. 4 vs hundreds.

But you raise an interesting question - what is a fair warranty for an anchor. We don't have a warranty on chain, at all (maybe we should discuss warranty of chain?) We don't get a warranty on sails. Osmosis warranty is for a limited time.

Fortress offer a lifetime warranty for the Fortress model, not the Guardian - but they are very exceptional for any item, marine or elsewhere. They are not the norm.

Interesting issue.

Jonathan

 

[Neeves]

Baba,

Prompted by your experience I had a look at the ballast chamber of our A80. Ours looks fine - the lead is tightly sealed or attached to the retaining aluminium plate (it appear to be 'sort of' welded or alloyed to the aluminium with no evidence of a crack or joint). The lead appears to be cast into the chamber it has a 'wrinkly or wavy' visible surface (like frozen liquid).

I had another look at your picture - and wonder if the cause is actually corrosion. If there was Pb/Al corrosion I would have expected you to report some physical product of corrosion (and all 2 metal corrosion with aluminium I know of) a bubbly or foamy white material, sometimes powdery. Many of us have seen this sort of thing when we have stainless fittings attached to aluminium - without Duralac. Now Pb/Al corrosion might be different - but your crack is clean.

Your crack is a straight lines and looks to me like a weld failure - why it has failed (apart from being a poor weld - I cannot guess (you will know better). Its straight along the seam and there are no white salts, of corrosion. Corrosion may have exascerbated any failure, that you missed (the crack) in the preceding weeks (or months) - but I would expect the corrosion to initially start at the exposed surface of the lead in the ballast chamber at the Pb/Al interface. The worst of the crack appears in the 'middle of the length of the weld, again I'd expect the failure to be seen at the surface of the ballast chamber and then grow toward the toe. If there wa a pin hole though which the water entered - I'd again expect the crack to be filled with powder - you would need a lot of white powder to generate that crack.

Now if you have white salts foaming from the ballast chamber then my idea is incorrect - but it seems more plausible given the crack that is visible. I'd also expect to see the aluminium itself to have other holes, cause by corrosion - not just the failure along the weld.

This does alter your approach to Spade - it might be poor manufacture (the unsupervised apprentice and poor quality control) rather than corrosion.

It might also bang on the head the shrill and repetitive cries of galvanic corrosion that looks questionable (in the absence of further information - but why spoil another good story - that will become more true by constant repetition.

There are many with much more experience of galvanic corrosion than me (and I have never seen Pb/Al corrosion - I doubt many have) - I'm not even a gifted amateur. But I'd like causes of failure to be correctly defined and not being incorrectly classified.

I did take advice on this from a professional welder in N America, who has also never seen Pb/Al corrosion - but like me has seen other dis-similar metal corrosion with aluminium.

There are people with much more expertise than me (us) and possibly they can offer a more educated analysis.

Jonathan

 

[vyv_cox]

Baba,

Prompted by your experience I had a look at the ballast chamber of our A80. Ours looks fine - the lead is tightly sealed or attached to the retaining aluminium plate (it appear to be 'sort of' welded or alloyed to the aluminium with no evidence of a crack or joint). The lead appears to be cast into the chamber it has a 'wrinkly or wavy' visible surface (like frozen liquid).

I had another look at your picture - and wonder if the cause is actually corrosion. If there was Pb/Al corrosion I would have expected you to report some physical product of corrosion (and all 2 metal corrosion with aluminium I know of) a bubbly or foamy white material, sometimes powdery. Many of us have seen this sort of thing when we have stainless fittings attached to aluminium - without Duralac. Now Pb/Al corrosion might be different - but your crack is clean.

Your crack is a straight lines and looks to me like a weld failure - why it has failed (apart from being a poor weld - I cannot guess (you will know better). Its straight along the seam and there are no white salts, of corrosion. Corrosion may have exascerbated any failure, that you missed (the crack) in the preceding weeks (or months) - but I would expect the corrosion to initially start at the exposed surface of the lead in the ballast chamber at the Pb/Al interface. The worst of the crack appears in the 'middle of the length of the weld, again I'd expect the failure to be seen at the surface of the ballast chamber and then grow toward the toe. If there wa a pin hole though which the water entered - I'd again expect the crack to be filled with powder - you would need a lot of white powder to generate that crack.

Now if you have white salts foaming from the ballast chamber then my idea is incorrect - but it seems more plausible given the crack that is visible. I'd also expect to see the aluminium itself to have other holes, cause by corrosion - not just the failure along the weld.

This does alter your approach to Spade - it might be poor manufacture (the unsupervised apprentice and poor quality control) rather than corrosion.

It might also bang on the head the shrill and repetitive cries of galvanic corrosion that looks questionable (in the absence of further information - but why spoil another good story - that will become more true by constant repetition.

There are many with much more experience of galvanic corrosion than me (and I have never seen Pb/Al corrosion - I doubt many have) - I'm not even a gifted amateur. But I'd like causes of failure to be correctly defined and not being incorrectly classified.

I did take advice on this from a professional welder in N America, who has also never seen Pb/Al corrosion - but like me has seen other dis-similar metal corrosion with aluminium.

There are people with much more expertise than me (us) and possibly they can offer a more educated analysis.

Jonathan

A couple of points. The anchor shown on my website has pitting corrosion that looks very similar to the one in this thread. The cheeks had bulged as a result of internal corrosion, I cannot see whether this is the same on the OP's. The anchor on my site is the second that failed in the same way, despite an improvement made by Spade, which I understand was epoxy coating of the internal surface before pouring the lead. Spade most certainly stated that the cause was galvanic corrosion.

Second point - I cannot see how the area of the crack was formed. In both photos available to us the weld stops part way down the triangular section and is not visible at the crack in the OP's nor the uncracked (probably) one on my website. There may be an internal weld (unlikely) or it may simply be folded in this area.

 

[Neeves]

I am not in any way arguing with any diagnosis on previous failures. I'm only addressing the current thread.

Though

I don't quite understand how coating with resin and then casting molten lead into the resin coated chamber would work - I'd expect the resin to simply oxidise. The alternative is that the lead was cast into moulds and the cast pieces resin bonded into the chamber - but you mention 'before pouring the lead'.

If the crack on the current anchor is caused by corrosion (whether its a failure of a weld or a weakness cause by a fold) - as you imply the pressures would need to be huge - yet there is no sign, in the photograph posted, of any sign of 'the products of corrosion that would be generated to produce that crack. No corrosion salts, nor indication of any build up of pressure - no bulge.

The crack is bigger half way along the crack - suggesting that whatever was impacting was focussed in that area - corrosion needs water, the entry for water is at the surface of the lead - far away from where the maximum stress appears to be.

I'm quite happy to accept it is folded, I have no axe to grind, (not welded) - but I'd still expect to see the salts of corrosion, I'd still expect to see some form of deformation. There has been no mention of either.

Jonathan