Cheminform, 1992

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Applied Surface Science, 2001

I investigate the corrosion behaviour of zinc in aerated neutral perchlorate solutions. Three different techniques, namely, potentiodynamic polarisation, potentiostatic current time transient, and electrochemical impedance spectroscopy (EIS), are used. The potentiodynamic anodic polarisation cyclic voltammetry curves exhibit an active/passive transition followed by pitting corrosion, con®rmed by SEM, due to the diffusion-controlled formation of a ZnO ®lm by the dissolution±precipitation mechanism. The cyclic voltammograms show an anodic peak AI and two cathodic peaks CI and CII. The peaks AI and CII are correlated to the formation and reduction of ZnO ®lm, respectively, and CI is attributed to the reduction of the pitting corrosion products. The potentiostatic current time transients at different electrolyte concentrations and applied potentials involve three stages: the ®rst involving ZnO layer growth, and the second and third involving pit nucleation and growth, respectively. The nucleation rate (t À1 i) increases with increasing electrolyte concentration and anodic applied potential. EIS shows an increase in the charge transfer resistance with applied potential near the anodic peak AI as a result of passive ®lm formation. At higher anodic potentials, the charge transfer resistance decreases as the applied potential approaches the breakdown potential E b. A nearly ideal Warburg tail of a dihedral angle of 458 is obtained, suggesting that the corrosion of Zn in NaClO 4 solution is controlled by diffusion in the passive range.

ICSC2023, 2023

Portland cement concrete production is associated with significant environmental impacts, as massive consumption of natural resources and responsibility for almost 6-7% of all the greenhouse gasses emitted worldwide. However, Alkali Activated Materials (AAMs) gives emissions of carbon dioxide up to nine times less and represents many characteristics of traditional concretes regarding mechanical performance and durability, despite their different chemical composition and reaction mechanisms, AAMs is relatively young material regarding available data crucial for durability and predicting the service life of reinforced AAMs such as chloride ingress properties, chloride diffusion coefficient or corrosion rate of reinforcing steels is limited. One of the most important aspects for reinforced structures deterioration is the corrosion in reinforcing steel bars. The life span of corrosion-affected uncoated reinforcing steel bars can be divided into three stages. I: from casting to the corrosion initiation. II: the damage state of the structures from the corrosion initiation to the end of serviceability. III: the safety state from the end of serviceability to the ultimate failure, this review provides a comprehensive review of previous studies focus on factors affecting stage I at AAMs related to Ordinary Portland Cement (OPC) as the rule of Ca/Si, anions concentration, incorporation of aluminium inside the C-S-H structure, types of used binder low-calcium/high-calcium fly ash (FA), Metakaolin (MK) or blended slag, effect of AAMs mix design ratios on its resistivity and hydration products, the effect of the chloride binding on gained compressive strength, and curing methods, even the chloride corrosion initiated due to the ingress of chloride ions during mixing or chloride ions diffusion through the cover. The review indicates the correlation of corrosion behaviour and physicochemical, derived structural and morphological characteristics which provides an overall insight into the electrochemistry of the corrosion process major characteristics.

Electrochemistry Communications, 2017

Zinc substrates were electrochemically oxidized in NaCl solution to produce corrosion patinas. XRD, XPS and Raman analyses enabled the identification of simonkolleite and zinc oxide as the patina constituents. FIB-SEM imaging shows that the upper part of the patinas is a network of simonkolleite nanosheets with an open microstructure that is unlikely to act as a significant barrier for corrosion processes. STEM investigations and Raman mapping measurements reveal the presence of a ca. 20-400 nm thin nanoporous ZnO-rich film below the simonkolleite and covering the zinc substrate. Under potentiostatic conditions, the reduced cathodic activity of the patina-covered zinc electrodes is assigned to this nanoporous ZnO layer.

Materials

Aluminum-based alloys have been considered candidate materials for cathodic protection anodes. However, the Al-based alloys can form a layer of alumina, which is a drawback in a sacrificial anode. The anodes must exhibit uniform corrosion to achieve better performance. Aluminum can be alloyed with Zn to improve their performance. In this sense, in the present research, the electrochemical corrosion performance of Al-xZn alloys (x = 1.5, 3.5, and 5 at.% Zn) exposed to 3.5 wt.% NaCl for 24 h was evaluated. Polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) were used to identify the electrochemical behavior. The microstructure of the samples before the corrosion assessment was characterized by means of X-ray diffraction analyses (XRD) and scanning electron microscopy (SEM). In addition, microstructures of the corroded surfaces were characterized using X-ray mappings via SEM. Polarization curves indicated that Zn additions changed...

Journal of Chemistry, 2013

The surface treatment of zinc was done with different concentrations of an oxime (2E)-2-(hydroxylamino)-1,2-diphenylethanol molecule by the immersion method. The electrochemical corrosion studies of surface-treated zinc specimens were performed in aqueous sodium chloride solution (1 M, pH 5.0) at different temperatures in order to study the corrosion mechanism. The recorded electrochemical data indicated a basic modification of the cathodic corrosion behavior of the treated zinc resulting in a decrease of the electron transfer rate. The zinc samples treated by immersion in the inhibiting organic solution presented good corrosion resistance. Using scanning electron microscopy (SEM), it was found that a protective film was formed on the surface of zinc.

Corrosion Science, 2007

The effect of sodium, calcium, and magnesium chlorides deposited on zinc and carbon steel surfaces was studied under atmospheric conditions. The cations strongly affected the corrosion rate of zinc, whereas they had a significantly lower impact on the corrosion of carbon steel. The corrosivity of cations of chloride salts for zinc increased in order of Mg 2+ < Ca 2+ < Na + . The higher corrosion resistance of zinc treated with calcium and magnesium chlorides was connected to prevention of formation of hydrozincite during zinc exposure in wet air. It was observed that zinc weight loss and the carbonate to simonkolleite ratio in corrosion products were correlating. The principal protective effect of bivalent cations can be seen in the decrease of pH of the surface electrolyte, which was caused by hydrolysis of such cations and subsequent formation of simonkolleite that blocked the cathodic sites.

Journal of Materials Science: Materials in Medicine, 2014

The effect of a systematic increase of chloride ion concentration on the electrochemical corrosion behavior of two types of Al-bearing TRIP steels (T 1 and T 2) was studied in aqueous NaCl solutions. Several electrochemical techniques were used comprising open circuit potential measurements, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Chloride concentration has a critical influence on the corrosion rate of the two tested steel samples. For both steels the corrosion rate first increased with increasing chloride content up to a certain critical concentration (CC), and then decreased in solution with chloride level higher than the threshold value. TRIP steel T 1 microalloyed with Nb and Cr as compared to steel T 2 not containing these two elements, exhibited lower corrosion rate and smaller CC value, indicating better corrosion resistance to chloride attack, albeit the Al content in T 2 is 220 times higher than that in T 1. This is because Nb alloyed with TRIP steel likely enhances the formation on the surface of a stable rust layer enriched with other passivating elements Al, Cu, Cr and Ni, which has higher corrosion resistance and hence improve greatly the passive performance of the TRIP sample. The ac impedance data are in good agreement with the OCP and dc polarization measurements. Surface examinations via scanning electron microscope confirmed well the obtained results.

Corrosion Science, 2016

A model electrode consisting of a narrow zinc anode and a split iron cathode was used for assessing galvanic corrosion at cut edges. This setup aimed at a better understanding of the mechanisms of galvanic corrosion at cut edges and of the effective resolution of microprobe electrochemical techniques, namely the scanning electrochemical microscope (SECM), the localized electrochemical impedance spectroscopy (LEIS) and the scanning vibrating electrode technique coupled with the scanning ion-selective electrode technique (SVET/SIET). Hydroxyl ions diffuse across the cathode, in the direction of the anode, until they reach the critical area of precipitation above the cathode, at a distance from the edge of the cathode. The zinc corrosion products ultimately precipitate on the iron cathode, once the critical pH and solubility limits for precipitation of zinc corrosion is reached, at a distance from the edge that is determined by the diffusion of Zn 2+ and counter-diffusion of OH-. These precipitates revealed no inhibition on the cathodic reaction. The local activity on the zinc was easily detected by the LEIS and the SVET, whereas the zinc corrosion products were detected by the SECM. The local a.c. admittance measured on the cathode closer to the zinc anode at the early stages was insensitive to the local activity despite the d.c. ionic current measured in solution, whereas for longer immersion times an increase of admittance is explained by an increase in the solution conductivity.

Corrosion Engineering, Science and Technology, 2011

Corrosion behaviour of nanocrystalline Zn-Ni alloy coatings (with 3 to 18 at-%Ni) electrodeposited on steel substrate from additive free chloride baths by DC plating has been investigated by measurement of open circuit potential with time and neutral salt spray test. The alloy coatings containing up to 16 at-%Ni exhibited an increase in resistance to the appearance of white and red rust with increasing Ni content. The resistance to the appearance of white rust and ability to protect the underlying steel substrate decreased with further increasing Ni content. This has been considered to be due to reduced passivating ability of the alloy coating with a significant rise in the grain size above 50 nm.