Restoring a rusty Spade anchor
Updated: May 20, 2020
One of the few eyesores when we bought our boat was our primary anchor. Spade anchors are considered among the best anchors available, but ours was showing signs of age with considerable surface rust but was still structurally sound. Replacing the anchor seemed unnecessary but finding a place that would hot-dip galvanized it again would be challenging for a relatively small item. So what to do? We decided to consult the experts.
After talking to the folks at Spade, we learned there was a more simple answer - cold galvanizing. A friend had a sandblasting box that would make quick work of cleaning the anchor to bare "white metal." Once the rust is eliminated and the surface prepped, we'd wash the anchor down with lots of acetone to remove any impurities on the surface, then apply several coats of ZRC cold galvanizing compound (pictured below).
A quart of ZRC cold galvanizing compound is relatively inexpensive and contains 95% pure zinc. When applied to a properly prepared surface, the effect on the metal is similar to that of galvanizing. You have to mix thoroughly and constantly to keep the zinc suspended in the medium.
Starting to work in the sandblasting box and ultimately getting the anchor back down to bare "white metal." The anchor looks transformed but not finished. Next we clean the surface and brush on several coats of ZRC compound. In the first image below, notice the first coat reacts with the bare steel and is evident from the dark grey color. Subsequent coats of the ZRC cold galvanizing compound dry to a flat, light grey color. Excessive build up is not necessary; we only applied three coats using a synthetic acrylic brush. Remember to use a mechanical stirrer to keep the zinc suspended while you apply it. We added a yellow gloss enamel on the top quarter of the anchor, which provides a visual aid to locate the anchor underwater and indicates depth of set.
We connected the anchor to our all chain rode with a Crosby class A anchor shackle (2.6 ton working load). Studies have proven this simple installation is more safe and secure than nearly all anchor swivels on the market, which cost more and will literally prove to be the weakest link in an otherwise solid ground tackle system. We've heard good things about the Mantus anchor swivel, but it's expensive and doesn't fit through our bow roller. The pin of the Crosby shackle is then secured with multiple wraps of high quality stainless mousing wire to the body of the shackle along with Loctite's blue thread lock. See pictures below of the final install.
We hope you find this approach helpful in restoring your anchor. If you don’t have access to a sandblaster, you can also use a wire brush attachment for a drill or even a sander with good results. We hope you’ll join our blog and follow along on our adventures aboard Koinonia!