In this paper Guard Ring Electrode was applied to study corrosion behavior of rebars in concrete. The current ratio of Counter Electrode (CE) and Guard Ring Electrode(GE) had been discussed during rebars were polarized. Furthermore, we discussed the effect of GE current for the sake of obtaining accurate polarization resistance Rp value. In order to achieve real Rp value, CE current must be confined in the projection rebar area below CE. During the experiment, the potential difference of concrete surface was monitored at the same time. However, it is insufficient considering only two-dimension current distribution. Generally very high concrete resistance tends to result in small measuring Rp value because of the over compensation of CE current. In order to obtain real Rp value, three-dimension other than two-dimension current distribution must be considered. Compared with uniform polarization result, it can be seen when rebars was active, CE polarization current could be confined preferably in the constant rebars area below CE by GEM, indicating the GEM could be used to monitor the corrosion behavior of rebars in concrete more accurately than other custom LPR method.

The natural corrosion potential,corrosion rate and steady-stat e polarization curves of Q235B carbon steel,TA2 titanium and navel brass in seaw ater were measured.The galvanic current,galvanic potential and galvanic corrosio n rate of anode and cathode of couple with different area ratio,at different tem perature and different velocity of seawater were measured.According to the data of the couple with different area ratio,a dynamic polarization curve of Q235B ca rbon steel was obtained.The galvanic corrosion characters of Q235B carbon steel /TA2 titanium and Q235B carbon steel/TA2 titanium/navel brass in seawater were invest igated.The results showed that corrosion rate of anode increased with increasing of area ratio of cathode/anode,temperature and velocity of seawater.But t here was a limited area ratio.The corrosion rate of anode did not increase when area ratio of cathode/anode was larger than the limit.When the galvanic co uple consists of the three metals,navel brass was cathode in the system and was protected by carbon steel.

Spark discharge is the representative phenomenon of micro-arc oxidati on (MAO) method.Accompanied with the spark discharge,the cell voltage presents oscillations within the range of several volts,and the surface morphologies,t he element distribution as well as the surface potential distributions of the an odic layer are significantly changed.It was found that spark discharges resulte d in a great deal of discharge pores in the oxide layer,accelerated the oxidati on and the deposition of electrolytic particles.Due to the melting effect of th e sparks,compact internal layer was formed underneath the outer loose layer,an d the surface potential over the spark zone was greatly enhanced.In addition,i t was found that oxygen played a key role in determining the intensity and the s ize of sparks,and abundant oxygen resulted in intensive and larger sparks.

Atmospheric corrosion of aluminium alloy was predic ted using BP neural network,and relation between training error and predicting e rror was researched.Artificial Heural network(ANN) model is composed of seven in put nodes,five hidden layer nodes and one output node.Correlation coefficient for model is 0.8821,ANN predi ction result is close to practical data.By sensitivity analysis method,metallurg ical factor and environmental factor influence for atmospheric corrosion rate of aluminium alloy was researched.

An investigation of the stress corrosion cracking resistance of 40CrNi2Si2MoVA high strength steel in typical atmospheric environment is presented. Direct tension and pre-cracked stress-corrosion specimens were used. The direct tension stress-corrosion specimens were taken from the longitudinal direction of stick and stress level was 65, 75, 85 and 95 percent of the σ0.2 respectively. The pre-cracked specimens were taken from the forging and applied constant load. The samples were exposed in Beijing, Tuandao, and Wanning atmospheric test station. The results showed that SCC performance of 40CrNi2Si2MoVA steel depend on the environments. High SCC sensitivity was expressed in marine environment. The SEM showed that the crack initiated from pitting corrosion in the surface and developed to inner of the samples. It is intergranular mode of cracking, secondary cracking existed on the fracture surface. Large size secondary cracking increases obviously with the higher of stress level. Serious corrosion was observed on the samples exposed in marine environment.

Micro-droplets phenomenon has a close relation with the electrochemical process of atmospheric corrosion.A volcano pattern of poten tial distribution with a potential valley in the center of main-droplet and a po tential annular peak in the area covered with micro-droplets was observed by sca nning Kelvin probe.The electrochemical polarization results proved that the spre ading rate of micro-droplets increased linearly with the polarization current,an d the corrosion current established by the potential difference between the cent ral and peripheral area of main-droplet was the true driving force for the forma tion and spreading of micro-droplets.

According to SEM observation,the corrosion regulati on of LC4 aluminum alloy with alclad in China water system and the protection of alclad on LC4 were studied.The corrosion experiment was done in seawater of Qin gdao,Zhoushan,Xiamen,salt lake with high salinity of Geermu,and fresh water of C hangjiang River in Hankou.The results of the corrosion experiment of two periods for half a year and one year show the protection of alclad on LC4 aluminum allo y was different because of different water.In seawater and fresh water,aluminum alloy was not corroded as the all protection of alclad.In salt lake,the alclad o n LC4 aluminum alloy remaindered for half a year,and used up for one year.The ba se of LC4 aluminum alloy was corroded seriously.

According to SEM observation,the corrosion regulati on of LC4 aluminum alloy with alclad in China water system and the protection of alclad on LC4 were studied.The corrosion experiment was done in seawater of Qin gdao,Zhoushan,Xiamen,salt lake with high salinity of Geermu,and fresh water of C hangjiang River in Hankou.The results of the corrosion experiment of two periods for half a year and one year show the protection of alclad on LC4 aluminum allo y was different because of different water.In seawater and fresh water,aluminum alloy was not corroded as the all protection of alclad.In salt lake,the alclad o n LC4 aluminum alloy remaindered for half a year,and used up for one year.The ba se of LC4 aluminum alloy was corroded seriously.

The influence of microbes adhesion on the passive s tate of high-Mo steel in natural seawater was studied.The conformation of biofi lm on metal surface was studied by epifluorescence microscope.And analyzed the c omposition of surface film with EDS.Results showed that the content of Cr in the passive film of stainless steel increased a little due to the formation of biof ilm.Polarization curves revealed that,in the earlier immersion time of high-Mo s teel,the longer time immersed in natural seawater for high-Mo steel,the more pos itive over-passivate potential and the less the passive current density will app ear.In other words,the formation of biofilms added the passive film stability of high-Mo stainless steels in natural seawater.

Variable microstructures of 1Cr19Ni23N electrode de posited metal were observed by scanning electron microscope and transmission ele ctron microscope.The effect of RE on intergranular corrosion resistance of auste nite deposited metal is discussed.The results showed that RE modified the micros tructure of deposited metal,and it has strong effect on the quantity,morphology and distribution of carbides.Intergranular corrosion resistance was increased o wing to the lessening of carbide particles formed at austenite grain boundaries and morphology changing from reticular to granular.

The corrosion of the La added medical 316L stainles s steel in physiological saline at 37℃ was studied by measurement of anodic pol arization curves.The results showed that the La content in 316L stainless steel greatly affects the corrosion behavior.The passive current densities were almost the same while the passive regions became wider with decrease of La content in the steel.The corrosion resistance of the 316L stainless steel with 0.04 mass% L a was equivalent to the 316L steel,with 0.01% La better,and 0.08% La worse.The s tudy shows that the corrosion behavior of the La added 316L stainless steel is m ainly due to the effect of La on the formation of passive film.

Galvanic corrosion behaviors of Q235-304L couple with various cathode/anode area ratios in three different concentrations of Na2S solutions were studied by the potentiodynamic polarization curves,galvanic method and immersion test.Surface morphologies of the samples were also analyzed by SEM after rust cleaning.The results showed that:both the cathodic and anodic processes of 304L were controlled by the electrochemical step,while the anodic process of Q235 exhibited an apparent characteristics of activation-diffusion mixed contro l;a cathodic process as well as an anodic process took place on the surface of Q235 after coupled and the dissolution current of Q235 was much more above the galvanic current got by galvanic corrosion method;as the area ratio increases,the galvanic effect increases;and with the elevation of the concentration of S2-,the corrosion rate of Q235 creased,so did the galvanic effect.

Applications of fractal theory in describing corrosion behaviors and creating co rrosion model were introduced based on the recent progresses in the field.Severa l successful samples were demonstrated in details,namely：(1) to correct the ind ex denoting corrosion fluctuation(e.g.,standard deviation)by fractal dimension ( FD) to better describing corrosion behaviors；(2) to observe fractal characteris tics on corroded steel surface (e.g.，distribution for micro-droplet formation i n early atmosphere and for pit diameter and depth in soil corrosion) and obtain distribution FD；(3) to propose a new approach to estimate 2-dimension FD(D2 D) and 3-dimension FD(D3D) of corrosion image and find that they respect ively denoted FD for pit diameter and depth distribution；(4) to create corrosio n formation model based on fractal dynamic process to predict corrosion developi ng of metals in soil and atmosphere，and display the parameter-relation between fractal model and experimental model.