Rust Never Sleeps – How to Identify the Right Cathodic Protection Company for Your Marine Structures and Assets

We Bluenosers understand the broad appeal of living and working by the seaside. The sweet smell of salt air and the kiss of ocean spray on your cheeks, harkens rolling sea shanties and an honest day’s work. 

But there are relentless challenges beyond the usual gales and tempests that accompany ocean life.  

Why Cathodic Protection Matters for the Marine Industry 

Corrosion, especially galvanic corrosion, is a silent destroyer of marine structures, equipment, and vessels.  

Fortunately, advancements in corrosion engineering—particularly cathodic protection—and with a little of bit of fore thought, your marine assets and modifications can be safeguarded against this corrosive force. 

From commercial fleets and shipyards, to offshore energy and naval defence, marine operators in Canada and around the globe require a reliable, certified and diligent cathodic protection engineer as a partner. With so many sailors among our ranks, we at Enginuity have unfortunately too often witnessed the devasting effects this corrosive phenomenon has on beautifully engineered marine assets. 

Intrinsic to Enginuity’s marine services is complete corrosion engineering. Whether you operate commercially, in research, or in the defence sectors, your corrosion protection requirement are the same. Learn more about our Marine Engineering Services to see how we can help protect your assets.

What is Galvanic Corrosion? (aka “Electrolytic Corrosion” or “Stray Current Corrosion”) 

Galvanic corrosion occurs when two dissimilar metals come into contact in the presence of an electrolyte, such as saltwater. This sets up an electrochemical reaction where the more reactive metal (the anode) corrodes, while the less reactive metal (the cathode) remains protected.  

The severity of galvanic corrosion depends on the position of the metals on the galvanic series. Metals like magnesium and aluminum are highly reactive, while stainless steel and gold are more noble (see fig 1). Pairing metals far apart on this scale—such as aluminum and stainless steel—can lead to rapid degradation in marine environments. 

Fig 1. This chart is used to determine the likelihood of corrosion and the electrochemical potential/nobility of elements. AG/AgCl (silver/silver chloride) electrodes are used as a reference.

“It [galvanic corrosion] can be incredibly dangerous and powerful if you get materials that are specifically terrible together like aluminum and stainless steel. You can eat away a piece of aluminum in days.” – Jean-Marc Guidon, Director of Engineering 

• What It Is: Occurs when two different metals are connected in the presence of an electrolyte (e.g., salt water), creating a battery-like effect. 

• The Mechanism: One metal becomes the anode (more reactive, loses electrons), the other the cathode (less reactive, gains electrons). The anode corrodes over time. 

• The Reactivity Rule: The greater the difference between metals on the scale, the faster corrosion will occur. 

Types of Cathodic Protection: A Proven Solution 

Cathodic protection (CP) is a cornerstone of corrosion engineering. It works by turning the protected metal into the cathode of an electrochemical cell, halting its corrosion process. There are two primary types: 

• Galvanic (Sacrificial) Anodes: These are made from highly reactive metals like zinc, magnesium, or aluminum. They corrode sacrificially to protect connected structures such as ship hulls or dock pilings. 
• Impressed Current Cathodic Protection (ICCP): This system uses an external power source to apply a continuous electrical current, ideal for larger or more complex marine.  

Here are four ways cathodic protection companies use to meet stringent technical, regulatory, and operational needs. 

1. Identify the vulnerable areas: Inspect hulls, tanks, propellers and submerged attachments for corrosion susceptibility.
2. Evaluate corrosion mechanisms: Consider galvanic, pitting, and crevice corrosion risks based on material composition.
3. Define the Design Parameters: What is the environmental conductivity(salinity)? What is the temperature range and the oxygen content and flow velocity in which your asset will be used?
4. Anode Type and Configuration: While aluminum and zinc are the most common choice for seawater, magnesium anodes are best used in freshwater. On hulls or near high-risk areas (thrusters and welds) it is best to install at equal intervals.

To determine the quantity of anodes needed, here’s a handy formula: 

Where Ic + current density, L =design life, Wa + anode weight,Ca = capacity 

Applications in Marine Engineering 

If you’re operating in or around water (especially seawater), cathodic protection systems are indispensable in protecting your marine structures and assets against saltwater’s corrosive effects. Common use cases include: 

• Ships and Boats: Sacrificial anodes are often attached to hulls to prevent corrosion. 

• Offshore Platforms: ICCP systems ensure the longevity of oil rigs and wind farms. 

• Docks and Piers: CP extends the lifespan of submerged metal supports. 

• Modifications: Any additional components added to the vessel require sascarifical anodes and often grounding straps. e.g. hull-mounted sonar deployment systems and davits. 

Two hull-mounted sonar deployment systems with grounding strap. Photo: Enginuity Inc.

Best Practices for Corrosion Prevention by Enginuity’s Daniel Horne 

For those familiar with cathodic corrosion, some things are obvious. However, Enginuity Mechanical Technologist and Team Lead Daniel Horne implores you to not overlook minimising the corrosive risks of marine environments: 

• Use uniform materials whenever possible. 

• Apply sacrificial anodes strategically and inspect them regularly. 

• Consider coatings as supplemental—not standalone—protection. 

• Please, do not paint your anodes! 

• Galvanising certain components can eliminate the efficacy of the protective circuit. 

• Fresh water and saltwater are different.  

• General rule of thumb – zinc for saltwater, aluminum for freshwater, avoid zinc in brackish water 

• A poor ground on your onboard electrical equipment can ruin it all. Use a good grounding(earth), protect with grease, Teflon, – polyether ether ketone (PEEK) is great stuff. 

An Enginuity SEALift SL-70 used for harsh marine launch and retrieval fitted with zinc anodes and PEEK screws.

“If you just paint or powder coat and you get a tiny pin hole in your paint, the corrosion is concentrated into that one tiny area.” –  Jean-Marc Guidon, Director of Engineering 

Next Steps & How to Engage 

Saltwater is unforgiving, but with proper planning and advanced technologies like cathodic protection, engineers can combat its corrosive effects effectively. By partnering with experienced cathodic protection companies and adhering to best practices in corrosion engineering, operators can protect their assets, reduce maintenance costs, and ensure safety in harsh marine environments. 

Whether you’re safeguarding a fishing vessel or maintaining offshore infrastructure, cathodic protection is your ally against the ocean’s relentless assault.  

Ready to protect your marine assets? Reach out to keep give your gear the long life they deserve.