Analytical calculation of the potential for contact corrosion of metals in the marine environment

One of the most common types of ship corrosion is contact corrosion, which occurs at the interface of dissimilar metals being washed. It poses a serious danger to the ship's hull and ship metal structures, as it leads to a sharp increase in the rate of corrosion damage to one of the contacting metals. Therefore, the fight against contact corrosion is one of the most urgent tasks in the field of anti-corrosion protection of ships. Protection of ships from contact corrosion requires solving a set of interrelated engineering problems that require a quantitative assessment of the rate of corrosion processes on ship structures and the effectiveness of anti-corrosion protection means used on ships [1, 2]. The article discusses an analytical approach in assessing the local rate of electrochemical corrosion processes of ship hull structures based on the phenomenon of polarization using polarization curves and approximation methods.

Protection enhancing of threaded connections of light-alloy drill pipes against contact corrosion

When using light-alloy drill pipes (LAIDP) with steel tool joints, the development of contact corrosion is observed under certain operating conditions. The value of corrosion mainly depends on the difference in electrochemical potential (ECP) of the contacting metals. One of the effective methods for increasing the corrosion resistance of aluminum alloys is the micro-arc oxidation (MAO) method. This is an electrochemical process in combination with micro-arc-discharges phenomena at the anode-electrolyte border, which allows forming ceramic coatings of aluminum oxides on the surface, including its high-toughness and wear-resistant phase - α-Al2O3 (corundum). MAO-technology is a highly efficient and environmentally friendly process. At the forming of such a coating on the threaded part and in the tool joint zone of the pipe, a barrier for contact corrosion between the steel tool joint and the surface of the aluminum pipe is created. In this work, contact corrosion on samples in a pair of 1953T1 aluminum alloy - 40KhN2MA steel in a 5% NaCl solution at 80 °C was investigated. The data obtained showed the effectiveness of using protective MAO-coating to reduce contact corrosion and increase the reliability of the tool joint threaded connection of LAIDP.

Soldering of steel sheets and zinc-coated aluminum by hybrid composite forging

In lightweight construction, light metals like aluminum are used in addition to high-strength steels. However, a welded joint of aluminum and steel leads to the precipitation of brittle, intermetallic phases and contact corrosion. Nevertheless, to use the advantages of this combination in terms of weight saving, composite hybrid forging has been developed. In this process, an aluminum solid part and a steel sheet were formed in a single step and joined at the same time with zinc as brazing material. For this purpose, the zinc was applied by hot dipping on the aluminum in order to produce a Brazing via these layers in a forming process, under pressure and heat. Due to the formed intermediate layer of zinc, the formation of the Fe-Al intermetallic phases and the contact corrosion are excluded. By determining the mathematical relationships between joining parameters and the mechanical properties of the joint, the strength of a specific joint geometry could be adjusted to reach the level of conventional joining techniques. In addition to the presentation of the joint properties, the influence of the joining process on the structure of the involved materials will be shown. Furthermore, the failure behavior under static tensile and shear stress will be shown.