Spade anchor corrosion

[SaltyMetals]

A friend gave me his old 25 kg (55lb) Spade which he said was the second Spade he changed after 6-7 years due to corrosion at the joint of the shank with the main anchor. I know the problems of re-galvanising a Spade due to the lead at the point so i reckon i can get many more years out of this anchor by cold zinc galvanising. I know the galv process very well and fully realise that cold galvanising is a very poor substitute but i think it might work.

However why is this happening all the time on Spade anchors? Apart from the fact that they should be giving their anchors a much thicker galv coat I suspect that it might be the stainless bolt that is used to lock the shank into the body of the anchor. How about i use a galvanised steel bolt instead of SS? My cold galvanising might have a better chance of surviving a few more years.

Some words of wisdom from you guys would be most welcome if you know this problem. I am not the first owner of this 25 kg Spade so have not contacted Spade directly.
Andrew

[tkeithlu]

I don't see an advantage. The galvanizing around the shaft is rough and brittle. A galvanized bolt will be likewise, and the two will abrade each other. The SS bolt is smooth, so while it will still wear, an argument can be made that it won't be as fast as galvanized/galvanized. What would really be nice would be a SS sleave that was fixed in the hole, with the SS bolt riding in it.

Other thoughts?

[ggray]

My boat came with a bridle with SS hook, SS thimbles, SS shackles, and right in the middle, several links of galvanized chain. The zinc disappeared quickly, sacrificed to the SS. I then removed all the SS.

I'd do the galvanized bolt, with a generous coating of Lanocote or grease. For the same reason, I wouldn't want a SS anchor.

[SaltyMetals]

tKeithLu,
I was hoping this thread would have flushed out some other Spade owners who had found other solutions.
I dont think the SS bolt takes much force. I think it is simply there to make sure the shank does not disconnect. The bolt on the 6-7 year old 25 Kg Spade that i was given is not worn at all. In fact the joint was totally jammed (by rust) and i had to get a local workshop to separate the shank so i could clean the joint down to bare metal. I have now given the whole anchor several coats of Zinc cold-galv spray with an additional 3-4 coats around the joint and inside where the lead is.
I am convinced that the rust problem is galvanic corrosion and that during manufacture Spade has not addressed this. I do not have any Lanocote onboard but i do have the British equivalent which is Duralac so will give the bolt, washers and nut a generous coating of this when i re-assemble the anchor. New anchors from Spade do not come with any such advice to prevent galvanic corrosion and my friend now says that he has had two 25kg (55lb) Spades and both of them rusted at about 6-7 years so has given up and gone for a different make of anchor since he lost confidence in the spade bec of all the rust at the joint even though i found it was mostly superficial. Although it would have gone rapidly downhill having lost its galv protection in the area of the joint. A pity bec i think the Spade is excellent as indeed Steve/"Panope" has shown in his excellent filming. A US$1,000 anchor should last more than 7 years. Now that i have fixed it there should be at least another 7-10 years of life in it. Possibly double that if i strip it once every 5 years and renew the Lanocote/Duralac on the SS bolt and zinc on the lead insert.
Andrew

[scherzoja]

I've been wondering about this also for my 55lb galvanized spade. What do y'all think about using G-10 rod with cotter pins and washers on each end? I'm kinda reluctant to use that because of possible chafing issues and I keep going back to heavily tef-gel/duralac/lanocote coated bolt, maintained frequently.

Regarding the bolt, assuming that tef-gel/duralac/lanocoat is maintained, which metal would be better:

Stainless: possible crevice corrosion issues.
Galvanized: Zinc wears off at chafe points, then rusts, but if properly coated, is that an issue?
Bronze: If coating is maintained, what issues exist?


https://www.mcmaster.com/rods/multip...g-10-fr4-rods/

[Benz]

I would butter up not only a galvanized bolt, but the entire mating surface of the shank/head with Lanocote, Duralac, or Tef-gel. It just makes sense to keep your metals similar.

[AA3JY]

Originally Posted by SaltyMetals

A friend gave me his old 25 kg (55lb) Spade which he said was the second Spade he changed after 6-7 years due to corrosion at the joint of the shank with the main anchor. I know the problems of re-galvanising a Spade due to the lead at the point so i reckon i can get many more years out of this anchor by cold zinc galvanising. I know the galv process very well and fully realise that cold galvanising is a very poor substitute but i think it might work.

However why is this happening all the time on Spade anchors? Apart from the fact that they should be giving their anchors a much thicker galv coat I suspect that it might be the stainless bolt that is used to lock the shank into the body of the anchor. How about i use a galvanised steel bolt instead of SS? My cold galvanising might have a better chance of surviving a few more years.

Some words of wisdom from you guys would be most welcome if you know this problem. I am not the first owner of this 25 kg Spade so have not contacted Spade directly.
Andrew

Have you talked to SpadeanchorUSA? https://www.spadeanchorusa.com/refun...nty-policy.php

We’ve had no issue with ours but have seen some really rough(rusted/corroded) versions at our marina..

[Panope]

I believe that the galvanized Spade anchor's stainless steel connecting bolt is an insignificant contributor to the premature corrosion of these anchors. Bolt is small compared to the other metals involved.

I believe that the galvanizing process used in the manufacture of these anchors is similar to other brands and is not a significant factor in the premature corrosion

I believe the dominate factor that leads to premature corrosion of Galvanized Steel Spade anchors is presence of a large amount of LEAD ballast that is in direct contact with the galvanizing AND is also immersed in an electrolyte (salt water).

Zinc (the primary ingredient of galvanizing), being the least Noble of the metals present in these anchors, will "sacrifice" itself to the lead (the most noble metal present). This "sacrificing" begins as soon as the anchor touches salt water.

I have owned two NEW Spade anchors along with about fifty other non-Spade anchors. The Spades are the only ones that begin to show galvanizing degradation soon after being put into service. Other anchors that do not have exposed lead but DO have stainless hardware do not show ANY corrosion or galvanizing degradation.

I do not believe that coatings or other treatments will cure this problem. One MIGHT slow down the corrosion progress, but once salt water gets in-between the lead and Zinc, the corrosion is unlikely to be stopped.

Premature corrosion is inherent to the galvanized Spade anchor design - A design that is excellent in almost every other way. It is not an anchor that can be reliably passed down through generations (I have my fathers 40 year old Bruce Anchor - looks perfect).

I recently snapped these photos of a "well traveled" spade anchor. Corrosion is what I would call severe and is progressing to the point where this anchor should soon be discarded. I believe the worst corrosion is happening "inside" the ballast chamber where the lead is in direct contact the the galvanizing and steel. I have photos of another Spade anchor where significant portions of the anchor's structure is entirely MISSING (rusted away).

[SaltyMetals]

You could be correct, Steve. When cleaning up my Spade i also gave the face of the lead filling a generous spray with Zn. The anchor i have had lost all the galv protection around the joint where the SS bolt is located within a radius of about 4", although i agree that the surface area of the SS bolt is quite small to have caused such a loss of the galv . There was also rust in the pocket just in front of the face of the lead filling. I had no rust on the upper surface as shown in your photo but i think that simply shows that the galv coating on Spade anchors is not very thick to start with. A pity bec the anchor performs very well when in use.

I have now coated the SS bolt with Duralac but i wonder if the face of the lead would benefit from being "painted" with Duralac as well.

I already had a 20 Kg (45lb) Spade but found i was having trouble in some weedy bays so decided to move up to a 25Kg (55lb). Recommendations for my boat seem to fall in the middle between the two anchor weights so i thought it was time to move up to the 25Kg and had an excellent opportunity when a friend gave me his old rusty 25kg(55lb).

Andrew
PS: I love your anchor series. Truly excellent. Bravo!

[markxengineerin]

Would a bolt on replaceable sacrificial zinc have any chance of helping this situation? I have a brand new spade anchor, hoping there is something to fix this problem and make it last like the 40 year old bruce.

Edit: what do other anchor manufacturers do differently to separate lead from galvanized steel?

[Panope]

Originally Posted by markxengineerin

Would a bolt on replaceable sacrificial zinc have any chance of helping this situation? I have a brand new spade anchor, hoping there is something to fix this problem and make it last like the 40 year old bruce.

Edit: what do other anchor manufacturers do differently to separate lead from galvanized steel?

A bolt-on "zinc" will have the same nobility as the zinc that is present in the galvanizing. Given that the galvanizing zinc has much more surface area and is in closer proximity (touching) to the lead, I would guess that a bolt-on zinc would have little benefit.

On every galvanic metal chart that I searched, the only metal that is less noble than zinc is Magnesium. Perhaps a Magnesium anode would offer some protection.

That said, if there was a simple solution to this problem, the Spade anchor manufacturer would have almost certainly already tried it.

I cannot think of any other Anchor manufacturer that uses lead ballast in their galvanized steel anchors. This is a Spade anchor problem only.

[markxengineerin]

Thanks, I wasn't aware that Spade was the only anchor with lead in galvanized steel.

How about just sealing the lead cavity so that salt water can't touch the lead? 4200 or 5200? If beauty is an issue, it would be easy enough to make something nicer looking out of a good plastic, still sealed up with something nasty though.

[AA3JY]

I have had the pleasure of conversing with Spade Anchors USA and they will be willing to share info concerning this and possible solutions.. Thank you Brian @ Spade USA

Regards,

Clay AA3JY

[SaltyMetals]

Steve, if you were to add a Mg anode i don't suppose it would last very long since not only would it sacrificially protect the Pb it will also sacrificially protect the Zn galv coat. It is for this reason that Zn & Mg anodes should not be used together on a boat. One or the other is fine, but not mixed.

So i wonder what Spade USA has been suggesting.
Andrew

[Franziska]

Originally Posted by Panope

A bolt-on "zinc" will have the same nobility as the zinc that is present in the galvanizing. Given that the galvanizing zinc has much more surface area and is in closer proximity (touching) to the lead, I would guess that a bolt-on zinc would have little benefit.



On every galvanic metal chart that I searched, the only metal that is less noble than zinc is Magnesium. Perhaps a Magnesium anode would offer some protection.



That said, if there was a simple solution to this problem, the Spade anchor manufacturer would have almost certainly already tried it.



I cannot think of any other Anchor manufacturer that uses lead ballast in their galvanized steel anchors. This is a Spade anchor problem only.

Unfortunately that's not true.

The, at least in Europe, popular Kobra anchor, which we are using and are generally very happy with, is also using a lead filled tip in the stainless and galvanized version.

Ours is also slowly using its galvanisation.

Advantage of the Kobra, it's got generally fairly good holding power and is reasonably priced.

Wonder if there is a way to create a similar anchor with the lead not cast in place but instead of this encapsulating it in some sort of plastic before placing it in the tip and somehow locking it in there.