Greater Corrosion Rate Research Articles

Corrosion Behavior of 316L Stainless Steels Exposed to Salt Lake Atmosphere of Western China for 8 years

The evolution of corrosion behavior of 316L stainless steels exposed to salt lake atmosphere for 8 years was investigated. The results showed that the stainless steel in salt lake atmosphere had a greater corrosion rate during the initial exposure time and relatively lower corrosion rate during the subsequent exposure time. Dust depositions accumulated on the downward surface caused severe local corrosion of stainless steel. As exposure time prolonged, the relative amount of Croxide and Feoxide in the corrosion products gradually increased, which may directly affect the corrosion rate of stainless steels. Moreover, the maximum pit depth followed a power function with respect to exposure time.

High-Capacity Dual-Electrolyte Aluminum–Air Battery with Circulating Methanol Anolyte

Aluminum–air batteries (AABs) have recently received extensive attention because of their high energy density and low cost. Nevertheless, a critical issue limiting their practical application is corrosion of aluminum (Al) anode in an alkaline aqueous electrolyte, which results from hydrogen evolution reaction (HER). To effectively solve the corrosion issue, dissolution of Al anode should be carried out in a nonaqueous electrolyte. However, the main cathodic reaction, known as oxygen reduction reaction (ORR), is sluggish in such a nonaqueous electrolyte. A dual-electrolyte configuration with an anion exchange membrane separator allows AABs to implement a nonaqueous anolyte along with an aqueous catholyte. Thus, this work addresses the issue of anode corrosion in an alkaline Al–air flow battery via a dual-electrolyte system. The battery configuration consisted of an Al anode | anolyte | anion exchange membrane | catholyte | air cathode. The anolytes were methanol solutions containing 3 M potassium hydroxide (KOH) with different ratios of water. An aqueous polymer gel electrolyte was used as the catholyte. The corrosion of Al in the anolytes was duly investigated. The increase of water content in the anolyte reduced overpotential and exhibited faster anodic dissolution kinetics. This led to higher HER, along with a greater corrosion rate. The performance of the battery was also examined. At a discharge current density of 10 mA·cm−2, the battery using the anolyte without water exhibited the highest specific capacity of 2328 mAh/gAl, producing 78% utilization of Al. At a higher content of water, a higher discharge voltage was attained. However, due to greater HER, the specific capacity of the battery decreased. Besides, the circulation rate of the anolyte affected the performance of the battery. For instance, at a higher circulation rate, a higher discharge voltage was attained. Overall, the dual-electrolyte system proved to be an effective approach for suppressing anodic corrosion in an alkaline Al–air flow battery and enhancing discharge capacity.

Effect of Time Voltage and Voltage of 1100 Aluminum Coating Using Chitosan Using Electrodeposition Method

Aluminum has mechanical properties such as light, easy to form, and the ability to conduct heat and electricity, but has less corrosion resistance properties. One effort to improve corrosion resistance in aluminum is by electrodeposition method. The electrodeposition process was carried out with a variation of time 10, 20, and 30 minutes and variations in voltage of 5 V, 10 V, and 15 V using AA 1100. The electrolyte used was a mixture of acetic acid and chitosan. Coating thickness measurement was carried out using NOVOTEST TP-1M coating thickness gauge, the corrosion rate was measured with 128N Autolab PGSTAT Potentiodynamic and surface roughness measurements using Mitutoyo SJ-210 Surface Roughness Tester. Based on the research data, it was found that the results of optimum layer thickness were obtained at 10 Volt variation of 20 minutes at 11 μm ± 0.04%. Specimens without treatment had the highest corrosion rate of 0.25541 mpy while the lowest corrosion rate was in the 10 variations of 20 minutes which produced 0.0078935 mpy. The surface roughness data of the specimen without treatment was 1.034 μm. The results of the smallest surface roughness were obtained at 10 V 20 minutes variation of 0.725 μm, while the largest surface roughness results in a variation of 15 V 30 minutes which was 2.529 μm. In this stud, it is known that the higher the time and stress used in the electrodeposition process results in greater corrosion rates, because it produces a higher layer thickness but results in higher surface roughness as well.

Corrosion kinetics and patina evolution of galvanized steel in a simulated coastal-industrial atmosphere

The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6SO4 are identified as the main stable composition and exhibit an increasing relative amount; while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops.

The Effect of pH Value on the Corrosion Behaviour of Ti-6Al-4V and 316L SS Alloys under Physiological Environment

The corrosion behaviour for stainless steel 316L and Ti-6Al-4V at pH 5.2 and 7.4 under simulated biological conditions either with or without the presence of proteins were investigated using electrochemical methods. The electrochemical tests were performed with and without the addition of bovine serum albumin (BSA) withconcentration of 10 g L-1 to the phosphate buffer solution (PBS) with two different phases of pH, which areacidic (pH 5.2) and neutral phase (pH 7.4) at 37 °C. The electrochemical methods used in this study were open circuit potential (OCP) and potentiodynamics polarization. The results of electrochemical tests showed that the corrosion potential (Ecorr) values of stainless steel at both pH values are slightly higher than Ti-6Al-4V in absence of BSA. The chromium (III) oxide (Cr2O3) film formed on stainless steel is more stable in neutral and also in acidic one without the presence of proteins. Meanwhile, the Ecorr of Ti-6Al-4V increases at acidic (-611.0 mV) and neutral pH (-585.0 mV) of human body in phosphate buffer solution (PBS) with addition of BSA, compared to test medium without the addition of proteins. This shows the interaction between proteins and surface of the Ti-6Al-4V have no significant effect onto its corrosion behaviour. However, the Ecorr of Ti- 6Al-4V at condition acidic pH with the absence of proteins, which is -740.0 mV showed the lowest corrosion resistance than stainless steel (Ecorr = -652.0 mV). In terms of corrosion rate values, stainless steel alloyshowed the best corrosion rate in neutral pH, which is 3.048 × 10-3 without addition of BSA in solution. But both alloys show greater corrosion rate at normal phase condition compared to acidic phase condition.

In Vitro Degradation Behavior of Ternary Mg-Zn-Se and Mg-Zn-Cu Alloys as Biomaterials.

In this study, the corrosion behavior of Mg-Zn-Se and Mg-Zn-Cu alloys was investigated to evaluate their corrosion behavior related to use as implantable biomaterials. The corrosion behavior of these alloys and a commercially available Mg-Zn alloy were examined using static solution electrochemical testing, dynamic solution gravimetric testing, ion leaching testing, and microscopic evaluation. Fluctuations in the pH of the Dulbecco's Modified Eagles Medium (DMEM) used for the gravimetric and ion leaching immersion testing were also recorded over the 30-day duration to assess whether the media conditions induced by the alloy degradation would permit for cellular survival. Weight loss experimentation and electrochemical tests revealed the Mg-Zn-Cu alloy to have the greatest corrosion rate.

Corrosion of cadmium plating by runway de-icing chemicals: Study of surface phenomena and comparison of corrosion tests

In this paper, we study the corrosion of cadmium plating by four runway de-icing chemicals using electrochemical measurements and standard (immersion) and proposed (cyclic) runway de-icing corrosion tests for cadmium plating. Besides the obtained electrochemical and gravimetric data, we analyze the exposed surfaces by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and infra-red spectroscopy (IR). The chemicals included in the tests are pure potassium formate, pure potassium acetate and the corresponding commercial chemicals.Examinations revealed two parallel and linked phenomena on the plating surface, i.e., anodic dissolution of cadmium and development of corrosion products, primarily cadmium carbonate, CdCO3. Electrochemical measurements disclosed that the formed corrosion products slightly improved corrosion resistance of the surface but definitely did not stop corrosion completely, probably due to discontinuous structure. As for the studied de-icing chemicals, potassium formates systematically introduced more segmented corrosion products than potassium acetates and, subsequently, more severe corrosion on the specimens. Immersion cadmium corrosion test did not give very reliable results due to relatively low introduced corrosion rates and very large occasional scatter in the results. Cyclic cadmium corrosion tests introduced relatively greater corrosion rates and somewhat lower deviations than the immersion test, being hence, more reliable, but also more challenging in terms of meeting the weight change criteria for passing the test.

Corrosion Study of some Metals in an Urban Atmosphere

This study essentially deals with atmospheric corrosion of metals like Iron, Copper, Steel and Aluminium. Eight different locations based on various activities were selected. The results are discussed as functions of the type of location, test material, and exposure time. The results indicate that iron and copper were prone to elevated corrosion, while steel recorded medium level and aluminum the least corroded. Among the locations, Maddilapalem emerged as the site with the highest effect on metals in terms of corrosion. Furthermore, greater corrosion rates were observed in the Rushikonda area, close to the coast followed by Gajuwaka and Kancharapalem sites. The results of the study can be used to obtain a corrosion fingerprint of the locations included in the study. The study provides an insight into the pollution effects on metals and their location specific activities with reference to corrosion which can be applied for suggesting alternatives or control methods.

The effect of deposits on waterwall corrosion in fossil fueled boilers

Corrosion of water walls in fossil fueled boilers and gasifiers has traditionally been considered the result of gaseous corrodants, such as H2S and HC1, reacting with the heat exchanger tube surfaces. Under reducing conditions these corrodants prevent the formation of a protective oxide scale, leading to increased metal loss. Recent field experience in boilers, using staged combustion systems, has shown much greater corrosion rates than predicted by simple gas/solid corrosion processes. The presence of large quantities of unoxidized iron sulfide in deposits in areas where high corrosion rates were found, suggests that deposits play a role as well. Subsequent laboratory corrosion studies found that the presence of FeS can indeed lead to very high corrosion rates, but only under oxidizing conditions. Since FeS usually deposits only where reducing conditions are present, the accelerated corrosion observed requires alternating reducing and oxidizing conditions. These are usually found in load following boilers. It is also shown that chlorine corrosion may be caused or at least accelerated by chloride containing deposits in fossil fueled boilers, similar to waste incinerators, where the role of chloride rich deposits has been well established. Due to the relatively high sulfur content of fossil fuels, chloride deposits most likely form under reducing conditions only. However, once formed they can be highly corrosive under oxidizing conditions.