Rocna and Vulcan anchors are made from galvanized steel or stainless steel. Both use a high tensile steel shank. We don’t build aluminum or titanium. Here’s the reason behind all of it.
Galvanized steel
Galvanized steel is what most anchors are made from, and it’s the most economical option. Ordinary steel gets a zinc coating, and the zinc corrodes instead of the steel underneath.
What buyers rarely see is how much the quality varies underneath that coating. Steel comes in grades, from mild through to high tensile, and the metallurgy varies within those grades. How the anchor is built matters too, whether it’s cast, forged, or fabricated from plate. Two anchors of the same shape and weight can be structurally very different.
Our approach is to build strength into the shape, so we’re not relying on the steel grade alone to carry the load.
The fluke has a single fold running down the middle. That fold continues into the narrowing tip, which is what keeps the tip stiff. If the fluke were formed as a simple curve with a large radius, the tip would flatten out as it narrowed and become the weak point, right where the anchor does its work. The skids reinforce the heel of the fluke. The heel is deliberately thinner than the tip, because we want the weight forward for setting. The roll-bar then ties the skids and the heel together, and the result is a very strong structure with no single member carrying the load on its own.
The shank is where anchors normally fail. It’s the long lever in the system, and it bends when a high lateral load is applied. The usual scenario is the anchor fouling on something on the bottom, an old cable or a rock crevice, and jamming while the boat pulls sideways on it. We use high tensile steel for the shank for exactly that case. It’s more expensive, and it’s not something we’re willing to trade away.
For the coating, the process matters as much as the zinc. It should be hot dip galvanizing, where the steel goes into molten zinc. Other methods deposit less zinc and give you a finish that won’t last as long. Rocna anchors are hot dip galvanized to a specification that exceeds industry standards.
Stainless steel
If cost isn’t the deciding factor, stainless is a practical alternative, and most people find it better looking. It also avoids re-galvanizing, which galvanized anchors eventually need once years of use have worn the zinc away.
Stainless is expensive, and it stays expensive relative to galvanized. Good raw material costs far more than ordinary steel, and the finishing work adds more again. If you find a stainless anchor that’s cheap, something has been given up getting there, and it’s usually the grade of steel.
Stainless comes in grades just as ordinary steel does, and the high material cost gives manufacturers every incentive to use the cheaper, weaker ones.
Many stainless anchors are built entirely from 316L. It’s the marine grade, and its corrosion resistance in seawater is fair. But its tensile strength is low, in the region of 280 MPa depending on sheet thickness, which makes it weaker than mild steel. A shank made from 316L is well under strength against any reasonable design criteria, and certainly against ours.
Every stainless Rocna has a high tensile shank. It’s costly and occasionally difficult to source. As with the galvanized anchors, we’re not compromising that component.
Finish is a separate question. Electropolishing is automated and low cost, and it produces a decent shine, but it leaves the surface uneven and won’t reach a mirror finish. Hand polishing is the only way to get there, and it takes a lot of hours, which is why it costs what it does. Sitting on the bow of a boat, many owners consider the result worth it. Like any stainless fitting, keeping that finish means polishing it by hand from time to time.
Why there’s no aluminum Rocna
Aluminum gives you more strength per kilogram, and it doesn’t need a protective coating. It’s also cheaper than stainless. The catch is volume. Aluminum plate must be thicker to match the strength of steel, so an anchor built to the same geometry in aluminum won’t be as strong, particularly when the steel version uses high tensile grades.
The bigger problem is that anchors want weight, especially at the tip. Weight is what drives the tip into the seabed. Lighten it and setting performance in sand, weed and grass suffers.
Aluminum is also softer than steel. The cutting edges of the anchor wear and deform, so performance falls off with use rather than staying put. The high strength hardened alloys give up corrosion resistance to get that strength, and any aluminum anchor sitting submerged for long periods brings galvanic corrosion into the picture.
We’ve had a look at what an aluminum Rocna would take, and it isn’t a straight material swap. The design would need substantial changes, and each of them cost performance. An aluminum shank can’t match the tensile strength of the steel one without getting thicker, and a thicker shank sets worse in hard seabed. That’s the trade we’re not prepared to make, so we don’t offer one.
What about titanium?
A very small number of titanium anchors exist. Titanium has broadly the same advantages and disadvantages as aluminum, all to a greater degree. It’s expensive even when you can source it, and it’s rarely an economical choice.
So, which should you buy?
Galvanized or stainless comes down to budget and appearance. The geometry is the same and the high tensile shank is the same, so you’re not choosing between strong and stronger.
→ Use the Anchor Selector to size the anchor for your boat, then pick the finish.