Effect on wear resistance of nanoparticles addition to a powder polyester coating through ball milling

Proceeding of: 13th Coatings Science International Conference (COSI 2017),The wear properties of a textured polyester powder coating with pyrogenic silica nanoparticles addition were evaluated. Raw powders of a commercial, textured polyester organic coating were mixed with low amounts of SiO2 nanoparticles (0.5&-3 wt%) using ball milling, a simple and economical method. Nanoparticles were mixed into the powder of thermoset organic coating for 10 min in a two-body planetary ball mill. Particle size distribution of the powder was measured to evaluate the milling effect. The coatings were applied and cured in an industrial installation on aluminum substrates. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the coatings were taken to analyze the homogeneity of the organic coating. Roughness, gloss and color were measured in order to evaluate their appearance. The effect of nanoparticles on abrasive and erosion wear performances was measured. Pin-on-disk wear tests were carried out. Erosion measurements were performed with free fall of sand on the samples, a test based on ASTM D968 standard. The results showed that the milling process provides a good distribution of nanoparticles as no agglomerates were found. The addition of 0.5 wt% silica nanoparticles allows for improvement of the wear resistance of the coatings.The authors acknowledge the financial support of Interreg SUDOE, through KrEaTive Habitat project (Ref. SOE1/P1/E0307

Influence of process parameters on the corrosion resistance of corrugated austenitic and duplex stainless steels

The main objective of this work is to study the influence of the forming process on two corrugated, lean, duplex stainless steels (DSSs): UNS S32001 and UNS S32304. Both grades have been recently proposed as alternative materials to the austenitic UNS S30403 grade for manufacturing reinforcement bars to be embedded in concrete structures, exposed to corrosive environments. Hot-worked (HW) corrugated bars of both DSSs are analyzed and their corrosion behaviour is compared with that of the HW and cold-worked (CW) corrugated bars of S30403. The corrosion performance is characterized through cyclic polarization curves in 8 different solutions that simulate those contained inside the pores of concrete in different circumstances. The obtained results justify a great interest in the studied lean DSS grades with respect to their use as reinforcements. Moreover, it is proved that the corrugated surface of a bar is clearly less corrosion resistant than the centre of the bar. The processing method of producing reinforcements influences not only the pitting susceptibility but also the pitting morphology.Publicad

Influence of the alkaline reserve of chloride-contaminated mortars on the 6-year corrosion behavior of corrugated UNS S32304 and S32001 stainless steels

This article belongs to the Special Issue: Corrosion and Protection of MetalsThe durability of two lean corrugated duplex stainless steel (UNS S32304 and S32001) bars manufactured for concrete reinforcement was studied in four different corrosive conditions. These duplex stainless steels are more economical than the most traditional, well-known duplex grade steels (UNS S32205). The research was carried out in mortar samples for six years. In half of the samples, the alkaline reserve had been previously decreased, and their pH was slightly below 12, while in the other half, the pH close to the bars remained as-manufactured. Moreover, there were samples with modified and non-modified alkaline reserve where chlorides had been previously added to the mortar which were exposed to high relative humidity. In other samples—which were partially immersed in 3.5% NaCl—the chlorides entered through the mortar by natural diffusion. The electrochemical behavior of the reinforcements in these conditions was periodically monitored through corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS) measurements during the whole testing period. The samples were anodically polarized at the end of the exposure. The results prove that the decrease in the alkaline reserve of the mortars can affect the corrosion behavior of the studied lean duplex in environments with high chloride concentrations. The duplex microstructure of the reinforcements makes it so that the corrosion proceeds by selective attack of the phases.This work was founded by the Ministerio de Ciencia, Innovación y Universidades of Spain through the project RTI2018-096428-B-I00

Welded, sandblasted, stainless steel corrugated bars in non-carbonated and carbonated mortars: A 9-year corrosion study

Three different stainless steel corrugated grades (UNS S20430, S30403 and S32205) were similar welded to stainless steel bars with the same composition and dissimilar welded to carbon steel (CS). After cleaning the welding oxides by sandblasting, the reinforcements were embedded in mortar with chlorides and some of the samples were carbonated. Corrosion activity was monitored using corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS). After 8 years of exposure, the samples were anodically polarized. Visual evaluation of the attack was performed after another additional year of exposure. Similar welded stainless steels offer a good durability if they have been sandblasted, except for S20430 when it is embedded in carbonated mortar with chlorides. Dissimilar welded steels are active since the beginning of the exposure for both studied conditions, but sandblasting reduces the corrosion rate of CS compared to non-welded CS bars.The present work was funded by the Spanish Ministry of Science and Innovation through the Project reference BIA2007-66491-C02-02

Influence of the forming process of corrugated stainless steels on their corrosion behaviour in simulated pore solutions

Stainless steels are formed by either hot working (HW) or cold working (CW) when used as reinforcement for concrete structures. The influence of the forming process on the corrosion behaviour is analyzed in depth in the present work. CW and HW corrugated bars of austenitic AISI 304L and 316L, and duplex SAF 2205 grades are studied. The electrochemical behaviour of the corrugated surface and the core of these materials are characterized by Mott Schottky analysis and polarization curves. Tests are carried out in both carbonated and non carbonated Ca(OH)2 solutions. The microstructure and local mechanical properties of these materials are also analysed by means of universal hardness (UH) measurements to complete available information. The results prove that the surface of corrugated bars is far more likely to suffer corrosion than the core of the same material. The corrosion probability and the morphology of the attack induced in corrugated surfaces by anodic polarization clearly differ in HW and CW bars.The authors wish to acknowledge the Spanish Ministry of Science and Innovation (through project BIA2007 66491 C02 02) for its financial support in this research

Influence of the microstructure of TMT reinforcing bars on their corrosion behavior in concrete with chlorides

Thermomechanically treated (TMT) carbon steel bars, often known as TempCoreTM bars, are commonly used as reinforcements in concrete structures. TMT causes the formation of a martensite case in the outer surface of the bars, increasing their hardness, while the remaining ferritic-perlitic core maintains the typical ductility of hot rolled bars. In this work, the effect of this TMT induced microstructure on the development of pitting attacks in chloride media has been analyzed in depth. Electrochemical impedance spectroscopy (EIS) measurements and polarization curves have been carried out in simulated pore solutions to understand the effect of the presence of different phases in the microstructure and to quantify the strength of the galvanic couple that the outer martensite can form with the inner core. Moreover, accelerated corrosion tests in chloride contaminated concrete slabs have been performed. Bars from six different slabs where corrosive attack has been forced for different times have been studied. The shape of the main pits in the bars corroded in concrete has been analyzed through optoelectronic microscopy and the results obtained prove that the depth of the attack is related to the microstructure of the TMT bars.The authors acknowledge the financial support of Interreg SUDOE, through KrEaTive Habitat project (grant Ref. SOE1/P1/E0307)

Corrugated stainless steels embedded in mortar for 9 years: corrosion results of non-carbonated, chloride-contaminated samples

Mortar samples reinforced with 5 different corrugated stainless steels were tested for 9 years in 2 different conditions: partial immersion (PI) in 3.5% NaCl, and chloride addition to the mortar and exposure to high relative humidity (HRH). The monitoring during the exposures was carried out with corrosion potential (E-corr) and electrochemical impedance spectroscopy (EIS) measurements. A year before finishing (after 8 years of exposure), the reinforced mortar samples were anodically polarised to obtain more information about the pitting resistance of the passive layers formed under the different conditions. The last year of exposure was established to study the progress or repassivation of the pits. The PI is the most aggressive testing condition and it causes low-intensity corrosion in S20430 austenitic stainless steel after 7 years of exposure. The S32205 duplex stainless steel shows very good corrosion behaviourThe present work was funded by the Spanish Ministry of Science and Innovation through the Project reference BIA2007 66491 C02 02

Hybrid cements: towards their use as alternative and durable materials against wear

Hybrid cements (HC) are a possible replacement of Portland cement, as their activation process only requires a small amount of sulphates, and is carried out with water at room temperature. The present work aims to study the wear behaviour of HC manufactured from two different wastes: blast furnace slag (HS) and fly ash (HFA). Their wear behaviour was compared to Portland cements (CEM I and CEM IV). Reciprocating wear tests and rolling wear Böhme tests were carried out for pastes and mortars, respectively. Wear tracks in the pastes were analysed through opto-digital microscopy and electron microscopy (SEM). In the mortars, the mechanical resistance was measured to understand different behaviours. The results obtained reveal that HC pastes and mortars present lower wear losses than CEM IV and similar to CEM I.This work has been supported by the Madrid Government (Comunidad de Madrid) under the Multiannual Agreement with UC3M in the line of "Fostering Young Doctors Research" (HORATSO-CM-UC3M) in the context of the V PRICIT (Regional Programme of Research and Technological Innovation), and by the Ministerio de Ciencia, Innovación y Universidades of Spain through project RTI2018-096428-B-I00

Use of licorice plant extract for controlling corrosion of steel rebar in chloride-polluted concrete pore solution

The possibility of using licorice extract as a green inhibitor for steel reinforcements in chloride-contaminated simulated concrete pore solution was explored in this study. Different licorice amounts were added to alkaline solutions and then 1% NaCl was also added. Electrochemical studies, up to 24 h, and surface analysis (X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy) were performed. Results demonstrated the inhibition effectiveness of the plant extract on steel rebar corrosion, regardless of the concentration, being detected an inhibition efficiency higher than 80 % with electrochemical techniques for 0.1% licorice extract, which showed the most effective performance. Surface analysis methods confirmed the presence of licorice on the surface, through the deposition of organic molecules present in the plant extract on the surface oxide/hydroxide. DFT calculations confirmed that compounds present in licorice can be chemically adsorbed on steel oxide surface.This research was funded by the European Union Horizon 2020 research and innovation MSCA-IF-2019 programme under grant agreement No 892074 (NATCON project). Support from the Ministerio de Ciencia, Innovación y Universidades of Spain (RTI2018-096428-B-I00) is also acknowledged

Carbonatación de morteros de escoria activados alcalinamente e híbridos: estudio mediante microscopía Raman Confocal y la repercusión en las prestaciones de desgaste

This work aims to contribute to reducing environmental damage caused by the manufacturing of Portland cements (PC), through in-depth exploration into the durability of two mortars manufactured from blast furnace slag: an alkaline-activated one (AAS) and a hybrid cement (HS) with less than 20% clinker. The carbonation resistance of these eco-friendly mortars is compared to that of a mortar based on Portland IV cement. From a mineralogical point of view, DTA-TG and confocal Raman microscopy (CRM) tests have been carried out, along with measurement of pH changes, compression strength and total porosity. Böhme tests have been performed to evaluate changes due to carbonation in the wear behavior of the mortars under study. Using the CRM technique, it has been possible to establish a relationship between the carbonation of the systems with the unbound carbon content, as well as identify the different polymorphic phases of CaCO3 formed. The results obtained reveal that alternative AAS and HS mortars are more difficult to carbonate than Portland cement mortars, and that the effect of this process on the porosity depends on the nature of the hydroxides previously present in the pore solution. The carbonation of the surfaces also improves the abrasive wear resistance of the mortars under study.This study was funded by the Ministerio de Ciencia, Innovación y Universidades of Spain through project RTI2018-096428-B-I00 and by the Madrid Government (Comunidad de Madrid) under the Multiannual Agreement with UC3M in the line of “Fostering Young Doctors Research” (HORATSOCM-UC3M) within the context of the V PRICIT (Regional Programme of Research and Technological Innovation).Publicad