Steel, Salt, and Survival: Real-World Strategies for Offshore Corrosion Protection
After more than twenty years of working on offshore platforms, I’ve seen my fair share of hard lessons—many of them the direct result of poor corrosion protection. One case that still sticks with me happened back in 2008: a platform in the South China Sea developed through-wall perforations on its support columns because the coating system failed. It took three months just to repair the damage, and the losses ran into the hundreds of millions.
So today, I want to talk about how we—those of us who’ve spent our careers building and maintaining steel structures at sea—deal with corrosion, our constant and stubborn adversary.
First Line of Defense: Coating Systems — Dressing Steel for Battle
People often think painting steel is just about aesthetics. In reality, there’s a whole science behind it. Our usual approach is a layered system, which I often compare to dressing someone for the cold and rain:
First layer: An epoxy zinc-rich primer, with about 85% zinc content. Think of this as the foundation—like prepping bare skin before putting on clothes.
Middle layer: A 200-micron coat of epoxy micaceous iron oxide. This adds a bit of insulation—like a good wool sweater.
Topcoat: A polyurethane finish, which serves as the waterproof outer shell.
But none of this matters if the steel surface isn’t properly prepared. We always require a Sa2.5 level of cleanliness—meaning clean, bright metal with no trace of rust or scale. You should be able to scrape it with a fingernail and not leave a mark. Just last year, during a major overhaul, we found that areas where surface prep had been rushed were already blistering after just three years. For steel structure buildings, the anti-corrosion methods are different.
Second Line: Cathodic Protection — A Steel Structure’s “IV Drip”
This method always reminds me of hospital IVs. We’ve used two main types:
Sacrificial anode systems—commonly aluminum blocks—are like hanging a saline drip. These need to be inspected regularly to make sure there’s still enough material left.
Impressed current systems—more like a machine-regulated drip—require external power and dedicated upkeep.
On a recent Bohai project, we tested a smart monitoring system that tracks cathodic protection in real time via mobile app. It’s reduced the need for underwater inspections significantly.
Choosing the Right Material — More Expensive Isn’t Always Better
I’ve seen projects where people jumped straight to stainless steel thinking it would solve everything, only to end up in worse shape. Here’s what experience has taught me:
For general areas, standard carbon steel with a solid protective system is usually the most cost-effective.
At critical joints, duplex stainless steel is a good option, but it requires meticulous welding to avoid long-term issues.
In splash zones, you’ll want to go with high-alloy steels that can handle constant wet-dry cycles.
Lessons from the Trenches
Back in 2015, we trialed a fancy new nano-coating. It performed beautifully in the lab. But after just three months offshore, it started peeling off in sheets. Since then, we’ve made it a rule: no new materials go into use until they’ve passed at least one year of real-world exposure testing in a marine environment.
Lately, we’ve been testing a self-healing coating that can seal minor scratches on its own—kind of like a liquid bandage. It’s promising, but honestly, nothing beats good maintenance practices. We run full inspections every quarter using drones combined with magnetic particle testing. It’s like a regular physical for the structure.
At the end of the day, corrosion prevention is a bit like staying healthy. There’s no miracle cure, no one-time fix. What works is a well-planned protection system, combined with consistent, disciplined inspection and upkeep. The knowledge we’ve gained came at a real cost—in time, in effort, and in money. I hope sharing it here helps others avoid some of the pitfalls we’ve learned to navigate.
