The marine environment is recognized as one of the most aggressive scenarios for metallic materials. The combination of physical, chemical and biological factors creates ideal conditions for the initiation and progression of corrosion. In marine structures, the severity of the corrosive attack is directly related to the zone in which the material is located. Four main exposure ranges can be distinguished: submerged, tidal, splash and atmospheric. <\/p>\n\n
The submerged zone<\/strong> corresponds to the portion permanently immersed in seawater. In this region, the corrosion rate tends to be more stable and relatively low, due to the limitation of dissolved oxygen. However, the accumulation of biofilms, marine incrustations and sediments can create microenvironments under the deposits, favoring localized corrosion processes such as pitting and corrosion under deposits. <\/p>\n\n The tidal zone<\/strong> is the area that is alternately submerged and exposed to the air, according to the movement of the tides. It is considered one of the most critical zones, as it combines intense oxygenation with the presence of concentrated salts during periods of emersion. This constant alternation promotes an accelerated wetting and drying cycle which intensifies the corrosive attack and favors the formation of deep pits and cracks. <\/p>\n\n The splash zone<\/strong> comprises the part of the structure that is constantly hit by waves and splashes, but which remains predominantly dry. Here, the continuous presence of salt droplets and the high concentration of oxygen create a highly corrosive environment. In addition, the mechanical impact of the waves can remove protective coatings, exposing bare metal and initiating rapid degradation processes. <\/p>\n\n Finally, the atmospheric zone<\/strong> includes those parts of the structure that are not directly affected by water, but are subject to the action of salt spray and condensation. Although less aggressive than the lower zones, this area also suffers corrosion, especially when there are deficiencies in the paint system or the presence of moisture retention points. <\/p>\n\n In addition to the physical characteristics of each zone, other environmental factors also influence the corrosiveness of the environment, such as:<\/p>\n\n A thorough understanding of these zones and the conditions that accelerate corrosion is essential for the correct design of protection systems, material selection and inspection planning. Below, we will explore the specific corrosion mechanisms that act in these environments and the types of failures commonly observed. <\/p>\n\n Uniform corrosion<\/strong><\/p>\n\n This is the most common type and, in general, the most predictable. It occurs when the metal surface undergoes homogeneous degradation, with continuous loss of thickness over time. Although it can be controlled by corrosion rate and over-thickness calculations, uniform corrosion can become critical when there is no continuous monitoring or when design data does not reflect actual environmental conditions. <\/p>\n\n Localized corrosion (pitting)<\/strong><\/p>\n\n This is one of the most dangerous mechanisms, as it causes the formation of small, deep holes (pites) that are difficult to detect visually. Pitting can quickly go through the thickness of the material, generating abrupt failures. They are more common in areas with salt deposition, solid deposits or anaerobic microenvironments, such as in the tidal zone and under biofilms. <\/p>\n\n Galvanic corrosion<\/strong><\/p>\n\n This occurs when two metals of different electrochemical potentials come into electrical contact in a conductive medium, such as seawater. The less noble metal (anode) suffers accelerated corrosion, while the more noble metal (cathode) is protected. This type of corrosion is common at connection points between different materials, for example carbon steel screws in stainless steel structures, or aluminum brackets attached to steel pipes. <\/p>\n\n Hydrogen-induced stress corrosion (HE-SCC)<\/strong><\/p>\n\n This mechanism combines chemical corrosion and mechanical stress, leading to the formation of stress cracks. In the marine environment, the presence of atomic hydrogen (generated by cathodic reactions or reducing microorganisms) can diffuse into the metal and cause embrittlement. This is particularly worrying in critical fasteners such as bolts, load-bearing brackets and welds, where residual stresses and hydrogen coexist. <\/p>\n\n Erosion-corrosion<\/strong><\/p>\n\n This phenomenon occurs when fluids flow at high speed over the metal surface, such as in piping systems or underwater ducts. Friction removes the natural protective layers or coatings, exposing the metal to corrosive attack. It is common in pipe bends, valves, fittings and places of turbulence. <\/p>\n\n Corrosion under deposits and biofouling<\/strong><\/p>\n\n The deposition of particles or the growth of marine organisms on the metal surface creates different environments where oxygen is consumed more quickly, forming differential corrosion cells. This favors both localized corrosion and the acceleration of general corrosion at the interfaces between covered and uncovered areas. <\/p>\n\n Each of these mechanisms can act alone or in combination, aggravating the process of structural deterioration. Early detection and precise characterization of the type of corrosion involved are essential for the success of corrective actions and the development of effective prevention strategies. <\/p>\n\n Corrosion in offshore structures is not just a matter of material degradation, it represents a systemic risk that compromises operational performance, increases costs and jeopardizes the safety of people, the environment and industrial assets. Below, we explore the main consequences observed in practice. <\/p>\n\n Loss of structural integrity<\/strong><\/p>\n\n The weakening of metal components due to progressive loss of thickness or the formation of corrosion cracks can compromise the stability of structures, piles, tanks, walkways and other critical parts of infrastructure. This can result in deformations, partial collapses or catastrophic failures, especially when corrosion occurs locally and silently, without obvious visual signs. <\/p>\n\n Operational interruptions and increased costs<\/strong><\/p>\n\n Undetected or poorly monitored faults often lead to the need for emergency stoppages for repairs, with a direct impact on production. On oil platforms, for example, this can mean millions of dollars lost every day. In addition, the cost of corrective repairs, which involve complex logistics (support boats, divers, cranes, ROVs), is significantly higher than that of preventive measures. <\/p>\n\n Risks to human and environmental safety<\/strong><\/p>\n\n Structures compromised by corrosion pose a real danger to workers’ lives. Falling walkways, ladder failures, explosions caused by leaks from corroded tanks and partial collapses are just a few examples of documented events. In addition, corrosion in pipes and tanks can lead to hazardous substances leaking into the ocean, generating severe environmental impacts and legal penalties for operators. <\/p>\n\n Reduction in the useful life of assets<\/strong><\/p>\n\n When not treated efficiently, corrosion accelerates the obsolescence of structures. Vessels that could operate for decades become economically unviable after just a few years of service, requiring premature replacement or decommissioning. This generates a cycle of unplanned investments, shortening the return on invested capital. <\/p>\n\n Institutional image and reliability of the operation<\/strong><\/p>\n\n Companies that face recurring failures associated with corrosion can suffer reputational losses and lose competitiveness in tenders and contracts. In addition, operators of offshore fields are frequently audited by regulatory bodies and insurance companies, which penalize the absence of integrity control with demands for more expensive policies or operational limitations. <\/p>\n\n Financial impact indicators<\/strong><\/p>\n\n Studies by NACE International estimate that the global cost of corrosion exceeds US$ 2.5 trillion per year, with approximately 20% of this figure related to the oil, gas and maritime transportation industry. The good news is that, according to the same studies, more than 30% of these costs can be avoided with systematic prevention strategies. <\/p>\n\n These impacts demonstrate that corrosion must be treated not just as a technical problem, but as a strategic factor that requires robust integrity policies and consistent investment in preventive engineering.<\/p>\n\n Given the aggressive nature of the maritime environment and the high cost associated with structural failures, corrosion control in offshore structures requires an integrated approach that combines technology, continuous monitoring and strategic planning. Prevention is always more effective, and economically viable, than correction. The following are the main strategies adopted in the industry: <\/p>\n\n Cathodic protection<\/strong><\/p>\n\n One of the most widely used techniques in submerged structures, cathodic protection consists of reducing the electrochemical potential of the base metal, making it cathodic and therefore immune to oxidation. There are two main methods: <\/p>\n\n Industrial coatings and painting<\/strong><\/p>\n\n The application of anti-corrosion paint systems is essential, especially in atmospheric, splash and tidal zones. The most effective coatings combine zinc-rich epoxy primers, barrier interlayers and UV- and weather-resistant finishes. Proper application, with surface preparation, uniform thickness and inspections, is crucial for the durability of the system. <\/p>\n\n Material selection<\/strong><\/p>\n\n Whenever possible, choosing corrosion-resistant metal alloys is an important preventative measure. Stainless steels, nickel alloys or titanium, for example, offer greater resistance in highly aggressive environments, albeit at a higher initial cost. In critical fastenings (such as bolts and structural supports), replacing carbon steel with more noble alloys can prevent failure due to HE-SCC and pitting. <\/p>\n\n Predictive maintenance and integrity management<\/strong><\/p>\n\n Risk-based maintenance programs (RBIM) assess criticality, probability of failure and consequences, prioritizing the most vulnerable assets. Periodic inspection, reapplication of coatings, scheduled replacement of anodes and updating of protection systems are essential steps to guarantee the integrity of the structure throughout its life cycle. <\/p>\n\n Training and preventive technical culture<\/strong><\/p>\n\n Finally, the effectiveness of any anti-corrosion strategy depends on the training of the teams involved. From design to operation and maintenance, all professionals must understand the risks of corrosion and the prevention methods available. Adopting international standards (such as ISO 12944, DNV-RP-B401, NACE SP0169) strengthens the culture of integrity and reduces technical errors. <\/p>\n\n These strategies, when applied in a planned and integrated manner, result in increased operational reliability, longer asset life and significant cost savings over time.<\/p>\n\n Finally, corrosion in maritime structures is an inevitable but not uncontrollable process. Its presence, although silent and gradual, can compromise not only the integrity of critical assets, but also the safety of operations, the environment and the economic viability of offshore projects. As demonstrated throughout this text, maritime environments impose extremely aggressive conditions on metallic materials, requiring engineering strategies to take into account each exposure zone and each type of stress involved.<\/p>\n\n Effective corrosion management requires a multidisciplinary approach involving materials engineers, designers, inspectors, operators and managers. The adoption of solutions such as cathodic protection, quality coatings, continuous monitoring and predictive maintenance should not be seen as a cost, but as a strategic investment in operational continuity and long-term safety.<\/p>\n\n Bibliographic reference:<\/strong><\/p>\n\n MOSES, David. Corrosion Impact of Offshore Platforms, Structures, and Vessels<\/em>. Materials Performance<\/strong>, NACE International, Houston, Nov. 2020.<\/p>\n","protected":false},"excerpt":{"rendered":" The marine environment is recognized as one of the most aggressive scenarios for metallic materials. The combination of physical, chemical and biological factors creates ideal conditions for the initiation and progression of corrosion. In marine structures, the severity of the corrosive attack is directly related to the zone in which the material is located. 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