If you’ve been around boats long enough, you probably know that certain metals provide important protection. For example, the copper in bottom paint is highly effective at preventing growth, while anodes made of zinc, aluminum and magnesium protect other metals below the waterline.

During the past several decades, we have gained a greater awareness of the potential harm these metals can cause, starting with copper in bottom paints. More environmentally friendly coatings have been developed, and restrictions on the use of copper continue to expand. Now scientists are beginning to quantify the impact of aluminum, magnesium and zinc deposits in our waters from sacrificial anodes. A 2023 report about the Taiwan Strait concluded that a “reduction or death of invertebrates in forests and water, even the reproduction of fish and amphibians, are directly related to aluminum pollution.”

It seems reasonable to expect that a regulatory push may come next. At least one company, CMP Group, via its Martyr anode brand, is looking to get out in front of that with the SMartyr impressed current cathodic protection system. It protects against corrosion without creating metal deposits. This concept is likely new to most boaters, but larger commercial vessels have used ICCP to manage corrosion issues for some time.

Here’s a look at each approach and how they can apply to the recreational market.

Sacrificial Anodes

Sacrificial anodes protect submerged metals by utilizing the properties of a galvanic reaction. When two dissimilar metals are submerged in an electrolyte and connected to each other, a galvanic cell is created. A galvanic cell is, in simple terms, a battery. The cell has an anode, a cathode and an electrolyte. In the case of boats, the electrolyte for our cell is the waterway. The less noble, or more reactive, metal is the anode, while the more noble, or less reactive, metal is the cathode. A chemical and electrical process occurs, with the positively charged metal ions leaving the surface of the anode, and the electrons leaving the cathode.

In a galvanic cell, the anode corrodes faster than it would by itself. The cathode corrodes slower. This slower corrosion protects the nobler metals that are used to make propellers, rudders, shafts and submerged structure. Without sacrificial anodes in place, the least noble of the submerged metals will become the anode and experience accelerated corrosion.

Because the voltages created by the galvanic cell are quite low, sacrificial anodes must be well distributed throughout the protected areas and located close to the critical components. That’s why it’s typical for shafts, rudders and trim tabs to have anodes mounted directly on them, in addition to a centrally mounted diver’s plate.

ICCP

Impressed current cathodic protection relies on an external source of regulated direct current power to polarize the surface that needs protection. As with sacrificial anodes, the controlled introduction of current turns the protected metals into cathodes, to reduce the corrosion rate of those important metals. This protective current is commonly distributed by mixed metal oxide anodes.

Unlike sacrificial anodes, the MMO anodes have long lives. MMO anodes are described as dimensionally stable because the anode is not consumed while it provides cathodic protection current. Commercial MMO-coated titanium anodes have service ratings ranging from 10 to 40 years before replacement is required.

ICCP systems have been used on commercial ships since the 1980s with great success. Commercial-vessel ICCP systems typically rely on alternative current rectifiers to provide the required DC power.

Until now, these systems have not scaled down to recreational boats . The need for AC power and extensive wiring through the boat isn’t practical.

SMartyr Refactors

SMartyr ICCP anodes are designed to provide the benefits of ICCP to the recreational market without the size, complexity and requirements of a commercial ICCP system. SMartyr anodes are small, self-contained systems with the MMO anode, control system, rectifier, battery and a solar panel all built into a single enclosure.

The first SMartyrs are intended to replace trim tab sacrificial anodes. The unit is a little bigger than a traditional anode and protects up to 3 square feet of submerged metal. Nearly the entire face is occupied by a high-efficiency solar panel designed to harvest enough energy from underwater, reflected light to power the unit for as long as three years.

At the end of the product life cycle, CMP aims to offer recycling options to help minimize ecological impact. Maintenance is expected to consist mostly of occasional cleaning to keep the solar panel and MMO clear of growth.

According to CMP Group, the trim tab-sized SMartyr will retail for about $230. At that price, it should compete with traditional sacrificial anodes over a three-year time span. However, the boat owner should experience savings from reduced labor expenses, since there will be no need for a yard or diver to change out the anodes on a regular basis.

SMartyr has the potential to improve the ecological footprint of boats and make boat owners’ lives easier, and maybe even a little cheaper. If all those promises can be met, it’s a good bet we will see more configurations of the SMartyr system and competing products from other manufacturers.

The journey from copper bottom paint to more sustainable options was filled with false steps and frustration. I am hopeful that the journey toward a more sustainable corrosion protection system will be smoother.