Higher manganese content strengthens microalgae inhibition in Cu–Mn steel coatings

Laser-cladded copper–manganese coatings on Q235 steel maintained low microalgal coverage after 180 days in algae-containing seawater, with the coating containing 20 wt% manganese recording the lowest attachment rates: 5.81% for Chlorella and 2.52% for diatoms. The findings indicate that raising manganese content from 10 wt% to 20 wt% helped preserve the coatings’ long-term antifouling performance by promoting the release of copper ions and increasing oxidative stress in attached microalgae.

The study examined how manganese content affected the corrosion behavior of three Cu–Mn cladding layers fabricated on Q235 steel. The layers contained 10 wt%, 15 wt%, or 20 wt% Mn and were immersed for 180 days in seawater containing Chlorella or diatoms. All three compositions showed low microalgal coverage, but the 20 wt% Mn layer produced the smallest values in both test solutions. The researchers attributed the improved inhibition to the structure of the corrosion-product layer rather than to a difference in the duration of testing: increasing manganese content promoted internal-stress accumulation, which accelerated cracking and flaking of corrosion products.

This mechanism matters because copper alloys are widely used in ships and marine engineering equipment for their antifouling performance. Over long service periods, however, the corrosion-product layer can become denser while microalgae attach to the surface, progressively degrading the material’s ability to resist fouling. In the tested Cu–Mn coatings, the corrosion products instead formed a loose, heavily cracked layer that could readily flake away. As manganese content increased, that layer became more susceptible to cracking and detachment, supporting continued copper-ion release into the surrounding water.

The released copper ions were linked to elevated intracellular reactive oxygen species, or ROS, in attached microalgae. The study’s proposed mechanism is that manganese-induced changes in the corrosion layer enhance copper-ion release, increasing oxidative stress within the organisms. The authors reported that the higher ROS level was associated with extensive apoptosis and effective suppression of attachment. The results therefore connect an observable coating behavior—cracking and flaking of corrosion products—with the biological endpoint of reduced microalgal colonization, although the supplied abstract does not provide the numerical copper-release or ROS measurements needed to quantify those intermediate steps.

The experiment provides a laboratory comparison of manganese content under a defined 180-day immersion period, rather than a direct field trial of coated marine structures. Its findings nevertheless offer a technically focused route for improving durable antifouling metal surfaces: adding more manganese to the Cu–Mn cladding changed the evolving corrosion layer in a way associated with stronger inhibition of two types of microalgae. The 20 wt% Mn composition achieved the best reported outcome, with coverage remaining at only 5.81% for Chlorella and 2.52% for diatoms, but the evidence does not establish how the coatings would perform across other organisms, exposure conditions or real-world service environments.

Subject of Research: Effects of manganese content on corrosion and microalgal attachment in Cu–Mn laser-cladded Q235 steel.

Article Title: Cu–Mn laser cladding layers on Q235 steel: the influence of Mn content on corrosion behavior and long-term microalgal inhibitory performance

Article References: Li, J., Liu, Z., Liu, J., Zeng, G., Wang, X., Yang, H., Ning, H., & Li, M. (2026). Cu–Mn laser cladding layers on Q235 steel: the influence of Mn content on corrosion behavior and long-term microalgal inhibitory performance. Journal of Materials Science, 61(41), 32076-32106. https://doi.org/10.1007/s10853-026-13665-0

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13665-0

Keywords: Cu–Mn coatings, laser cladding, manganese, Q235 steel, marine antifouling, corrosion products, microalgae, Chlorella, diatoms, reactive oxygen species, laser, cladding