Ma Shide

Corrosion of mild steel in different granularity seabed sediment saturated with seawater

In order to investigate the corrosion of pipeline materials in Seabed Sediment (SBS) environment, weight-loss and electrochemical measurements in saturated sand and mud cells with seawater were performed for a simulation. The used electrochemical measurements included linear polarization resistance (LPR) and potentiodynamic scanning measurement. It was showed that the corrosion rate of mild steel in the present condition was lower than the corrosion rate of other marine environment corrosion zones of it; that the granularity of SBS could affect the corrosion behavior greatly; that with increasing grain size of SBS, the corrosion rate increased. Integrated over the results of the weight loss and polarization curves, the oxygen diffusion (oxygen as a depolarizant agent) mechanism was proposed and discussed.

Electrochemical measurement of steel corrosion in seabottom sediment with “MD” method

The through one year corrosion potential and polarization resistance for 3 kinds of steels in seabottom sediment of Liaodong Bay were measured with the “MD” method.The measurements will have some theoretical and practical values. The theoretical value lies in that the recorded changing process of the practical corrosion case can be basis for indoor discussion and electrochemical research on the corrosion process. The practical value lies in that the obtained data can be basis for designing and controlling electrochemical protection systems. In fact, it is very difficult to measure in situ the corrosion parameters of steels in sea sediment.

Influence of active marine organic matter on electrochemical corrosion

Chemical means were used to extract polyphenols from healthy brown algae collected in littoral seawater. Experiments on corrosion of A3 steel, the time-potential curve, and polarization curve in polyphenols seawater showed stronger cathodic polarization compared with that in common seawater. This indicates that brown algae polyphenols might feasibly be used as corrosion inhibitor in seawater.

Effects of anaerobe in sea bottom sediment on the corrosion of carbon steel

This in situ corrosion study of steel in sea bottom sediment by the “Plate Transplanting Burying Method” (MD method) showed that the corrosion rate of steel in sea bottom sediment with sulfur reduction bacteria (SRB) can be as high as ten times that in sea bottom sediment without SRB. The experiments in simulating sea bottom sediments with different concentrations of cultured SRB showed that the electrochemical polarization behaviour of steel in sea bottom sediment with and without SRB were different. SRB altered the polarization behaviour of steel significantly by acidifying the environment so that apparent hydrogen depolarization occurred and accelerated the corrosion of steel.

Electrochemical corrosion behavior of hot dip coating in artificial seawater

The corrosion behavior of a zinc-based alloy (compared with that of pure zinc) coating was studied in this research on the electrochemical corrosion behavior of hot dip coating in artificial seawater. The electrochemical parameters of these two hot dip coatings were measured by the galvanostatic method and accelerated corrosion test. The two coatings showed uniform corrosion, but the corrosion of the pure zinc coating was actively sustained continuously. The corrosion of the zinc-based alloy coating was very slow because of the formation of a stable anti-corrosion membrane. The corrosion mechanisms of these two coatings were also compared by the weak polarization curve fitting method. The corrosion of the zinc-based alloy coating is typical of that in natural passive corrosion system.

Corrosion and adherence at sea oil-platform

Measurements of the adhesive corrosion and protective potentials of 3 Bohai Sea oil platforms under different cathodic protection showed corrosion still occurred on these platforms under their designed protective potentials. Preliminary conclusions from indoor experiments on the relation between adhesive corrosion and cathodic protection showed adhering organisms caused the corrosion on these platforms.