MMO Ribbon Anode

The submarine cable landing zone specifically refers to the transition section where the cable extends from deep-sea shoals to onshore trenches and base stations. It encompasses four major operational zones: the fully submerged underwater zone, the tidal zone subject to alternating wet and dry conditions, the wave splash zone, and the onshore salt-affected tidal flat zone. Each zone exhibits significant differences in corrosive media, corrosion rates, and modes of damage, forming a complex corrosion system characterized by multi-field coupling. This is the core reason why corrosion issues in this area are far more severe than in deep-sea sections.

In terms of the core mechanism of medium corrosion, the salinity of seawater in the landfall area remains stable at around 35‰, with chloride ion concentrations exceeding 50,000 ppm. Highly reactive chloride ions with small radii possess extremely strong penetrating and adsorbing properties, enabling them to easily penetrate microscopic cracks in the cable's outer sheath, destroy the passivation film on the surface of the metal armor and sheath, and induce localized pitting and crevice corrosion. At the same time, the alternating wet-dry cycles caused by tidal fluctuations subject the metal structures in the cable landing section to repeated transitions between "seawater immersion" and "air exposure."

Sediment accumulation can obstruct medium flow in localized areas of the cable, creating an oxygen-deficient corrosion environment that induces anaerobic bacterial corrosion; the metabolism of attached marine organisms alters the local pH environment, accelerating the failure of the metal passivation film; continuous scouring by waves and tides wears down the cable's outer sheath, enlarging pathways for corrosive media to penetrate; stray currents generated by coastal power grids and rail transit systems disrupt the polarization potential of metal structures, triggering stray current corrosion and causing rapid localized perforation and damage.

Submarine cables typically use steel wire armor structures to enhance mechanical strength, enabling them to withstand ocean current impacts, trawl netting, seabed sediment pressure, and installation tension. However, the steel wire armor layer is essentially carbon steel, which is prone to electrochemical corrosion in seawater. The corrosion process is: Fe → Fe²⁺ + 2e⁻. As the steel loses electrons, it gradually dissolves, reducing the wire diameter and decreasing mechanical strength. In the landing area, due to bending, vibration, and external friction, the armor layer is easily damaged locally, exposing the steel wires in direct contact with seawater, creating high-corrosion-risk areas. It continuously supplies electrons to the steel armor layer through an applied current, transforming the steel surface from an anodic corrosion state to a cathodic state. Its effects include reducing the rate of steel dissolution; reducing pitting corrosion formation; delaying the loss of cross-sectional area of ​​the steel wires; and maintaining mechanical load-bearing capacity. For long-term submarine cables, this electrochemical protection can significantly improve the lifespan of the armor structure.

Submarine cables typically require a metallic grounding system to ensure electrical safety, fault current release, and shielding protection. However, grounding structures often contain different metallic materials, such as copper, steel, stainless steel, titanium alloys, and carbon steel connectors. Different metals are prone to galvanic corrosion in seawater environments. For example, when copper and steel are connected, due to the difference in electrochemical potential, the steel material may become the corrosion anode, accelerating wear. MMO anodes can reduce the corrosion driving force between different metals by adjusting the overall system potential. Their application value is mainly reflected in protecting grounding connection points; reducing dissimilar metal corrosion; improving joint reliability; and reducing maintenance frequency. This is particularly important for long-term unattended submarine cable systems.