Defend carbon steel against corrosion by seawater

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An article published in the journal Chemistry and physics of materials described a unique method of improving the anticorrosive properties of carbon steel.

Study: Manufacture of a super-hydrophobic Ni-Co / Cu coating with better corrosion resistance. Image Credit: Guilbaud Stan / Shutterstock.com

The researchers used electroplating, chemical oxidation, and surface adjustment to create an ultra-hydrophobic Ni-Co / Cu nanocomposite lamination that can be applied to carbon steel surfaces.

Scanning electron microscopy (SEM), X-ray diffraction (XRD), and water contact angle assessments were used to study surface properties, structures and wetting characteristics. The results showed that the contact angle with water increased to 158.61 °, indicating an ultra-hydrophobic character.

Corrosion of carbon steel and how to prevent it

Due to its decent mechanical qualities and low cost, high strength carbon steel is frequently used in marine engineering. However, its low corrosion resistance even under moderate operating conditions limits its applicability.

Corrosion can reduce the load capacity by reducing its overall size or by pitting, resulting in economic losses and massive accidents.

Coating or preservation lamination is the most widely used anticorrosion technology among contemporary corrosion prevention technologies, which include cathodic shielding, anticorrosive materials, and coating. Electroplating is one of the most industrially feasible and cost effective processes for producing nanoscale metal matrix, alloy and metal matrix composite coatings.

Use of nickel-based nanocomposites

Nickel (Ni) is a popular type of electroplating metal. The main disadvantages of electrodeposited Ni include its low firmness and limited wear resistance.

Researchers have created nanoscale composite coatings based on Ni, such as Ni-CeO2 coating, to increase the performance of nickel coatings. Another way to improve Ni coating performance is to fabricate many alloy coatings. Due to its high resistance to wear and corrosion, the nickel-cobalt alloy (Ni-Co) layer created by electrochemical deposition is essential to protect carbon steel. Ni-Co alloy coatings are also more corrosion resistant than Ni coatings.

The inclusion of cobalt atoms causes a deformation of the solid solute framework and a decrease in porosity, which increases the corrosion resistance of the coating. However, the presence of defects such as pits and hemp points necessitates further improvement in the surface quality and anti-corrosion behavior of the nickel-cobalt coatings.

Ultra-hydrophobic Ni-Co lamination has piqued the curiosity of many in recent years due to its ability to prevent the penetration of corrosive substrates and provide superior corrosion protection.

It is generally recognized that the most important variables in the formation of a superhydrophobic surface are unique nanostructures and minimal surface energy. By modifying the surface with the help of organic compounds such as 1-dodecanethiol and silane, low surface energy can be easily achieved.

The construction of a good rough structure is a critical subject for research, and since more complex parameter control is required, obtaining a sufficiently rough nanostructure surface via electrochemical techniques is much more difficult. In addition, the creation of rough surfaces requires a higher surge voltage which can adversely affect the protective effectiveness of the coating.

The fabrication of rough microstructures greatly limits the practical uses of superhydrophobic surfaces. Accordingly, it is important to design a simpler method of making a rough structure on the Ni-Co lamination surface.

Electroplated copper and copper based alloys are widely used in a wide range of applications. The formation of nanostructures on the surface of copper to generate an ultra-hydrophobic influence has received a lot of attention.

Chemical etching is one of the most widely used processes to produce said nanostructures. It has the advantage of being easy to use and inexpensive.

In view of these advantages, a copper coating is used to provide Ni-Co with an ultra-hydrophobic characteristic.

A copper coating was electrodeposited over a Ni-Co lamination in this study, forming a Ni-Co / Cu composite coating which demonstrated super-hydrophobic properties after being treated with an oxidation solution and a dodecanethiol modification.

The advantages of this technology are as follows: (1) the high water repellency impact of the development of the Cu coated surface has been widely studied, and the procedure is reasonably easy; (2) the need to carry out rigorous control over the development procedure of the nickel-cobalt coating is eliminated. In addition, the surface hydrophilicity and corrosion resistance mechanism of the Ni-Co / Cu composite coating were examined.

To conclude

Ultra-hydrophobic Ni-Co / Cu lamination was created on a carbon steel substrate using a two-step electroplating process and dodecanethiol modification to increase corrosion resistance.

The results demonstrated that this approach could increase the protective capacity of Ni-Co coatings by preventing hostile media from coming into contact with the substrate, confirming the attractive practical potential of the technology in maritime environments. This technology offers a new way to improve the efficiency of Ni-Co coatings.

Continue reading: The potential of graphene as an ecological corrosion protection.

Reference

Lin, Z., Zhang, W., Zhang, W., Xu, L., Xue, Y., & Li, W. (2021) Manufacture of superhydrophobic Ni-Co / Cu coating with corrosion resistance improved. Chemistry and physics of materials. Available at: https://www.sciencedirect.com/science/article/pii/S0254058421012864?via%3Dihub

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