In order to reveal the corrosion of a ship hull in flowing seawater, which is difficult to study under experimental conditions, a numerical method was adopted. Firstly, the numerical model of seawater flow field around the hull was established and computed, and the hydraulic characteristics of the flow field such as velocity, pressure, and oxygen concentration distribution were got. The distribution of oxygen has a great influence on corrosion. Generally speaking, where the oxygen concentration is higher, the corrosion rate is higher. The results show that the oxygen concentration is higher at the rear of the hull bottom surface. Next, a corrosion model was founded based on the above calculation. Through the calculation of the corrosion model, the mass transfer coefficient and corrosion rate distribution on the hull surface were obtained and the final conclusion was got flow accelerated corrosion (FAC) mechanism was revealed. The conclusion is as follows: Comparatively speaking, the corrosion rate of the middle and rear part of the bottom and the middle part of the sideboard is higher. Generally speaking, the corrosion rate increases with the increase of flow rate.

A miniaturized diffuser/nozzle micropump with extremely thin (only 2.1 µm in thickness) polyimide (PI) membranes was fabricated on a 60-µm-thick Si wafer using simple photolithography processes. The diameter of the diaphragm was 2 mm, and the chamber depth was 60 µm. The micropump was functioned by deforming the membranes with alternating air pressure. The ethanol flow rate of the micropump was over 400 nl/min at 2.5 Hz with an actuated pressure of 5 kPa. The measured flow rate was relatively higher than those of previously reported micropumps with a similar chamber volume owing to the large deflection (over 40 µm) of the PI membrane. The micropump processing issues of plasma induced damage to the PI membrane during Si chamber etching and the behaviors of the static and dynamic deflections of the PI membrane was also discussed. On the basis of the advantages of photolithography processes and the good performance of the micropump, it is expected that the micropump can be fabricated on silicon integrated circuit chips.

The pipeline easily gets corroded in a seawater environment. The oxygen in the seawater is one of major parameters causing the corrosion. In practice, the corrosion due to the oxygen concentration difference, i.e. differential concentration corrosion (DCC), cannot be avoided. However, a one-dimensional DCC model cannot satisfactorily predict the corrosion because the oxygen distribution near the pipe wall is two-dimensional. In this regard, a two-dimensional DCC model was proposed in this study to numerically investigate the distribution of corrosion potential and current in the ionic conductive layer near the pipe wall as well as the overall corrosion current. The results show that DCC plays a significant role in determining the corrosion potential and current. Without considering DCC, a large corrosion potential and current exist at the location with high oxygen concentration near the pipe wall, whereas the occurrence of the low corrosion potential and current corresponds to the location with low oxygen concentration. However, as DCC is considered, at the location with high corrosion potential, cathodic polarization was produced and the corrosion rate decreases; at the location with low corrosion potential, anodic polarization was produced and the corrosion rate increases. In general, the corrosion potential can be homogenized in terms of DCC.