•The limits for LDX 2101® duplex stainless steel application in H2S-containing environments.•The susceptibility to SCC of LDX 2101® duplex stainless steel in the presence of Cl− and SO32-.•The ...possibility of substituting H2S with thiosulphate for the study of the SCC susceptibility.•The selective corrosion of ferrite phase during crack propagation process in the tested media.
SCC behaviour of a LDX 2101® stainless steel was studied through SSRT in a 20% NaCl solution at 80°C and in the standard NACE TM-0177 solution at 25°C in the presence of S2O32-. Some tests were also performed in the NACE solution at various pH or temperatures. The LDX 2101® was susceptible to SCC in the presence of small thiosulphate concentrations. The selective corrosion of the ferrite phase became the main cause of failure when the thiosulphate concentration was increased to 0.1M in the 20% NaCl at 80°C or when NACE solution temperature was raised to 80°C.
► The effects of anionic surfactant on AZ31 Mg alloy corrosion inhibition is studied. ► The influence exerted towards the anodic and cathodic processes is evaluated. ► An interpretation of inhibition ...mechanism is proposed. ► The influence of a precipitated layer on the anodic Mg oxidation is determined.
Gravimetric and electrochemical measurements were applied to study the inhibiting action exerted by some anionic surfactants (sodium salt of N-lauroylsarcosine, N-lauroyl-N-methyltaurine, dodecylbenzensulphonic acid or sodium lauryl sulphate) towards AZ31 Mg alloy corrosion in electrolyte solutions. The influence of the additive concentration, immersion time and type of surfactant was evaluated.
Their inhibiting effects was attributed to a rapid adsorption on the metallic surface, which limited the cathodic reaction, followed by a precipitation stage with Mg++ ions that made the inhibiting layer thicker and less defective, so that, over time, the anodic oxidation was almost blocked in a wide potential interval.
Architecting software systems according to the service-oriented paradigm and designing runtime self-adaptable systems are two relevant research areas in today's software engineering. In this paper, ...we address issues that lie at the intersection of these two important fields. First, we present a characterization of the problem space of self-adaptation for service-oriented systems, thus providing a frame of reference where our and other approaches can be classified. Then, we present MOSES, a methodology and a software tool implementing it to support QoS-driven adaptation of a service-oriented system. It works in a specific region of the identified problem space, corresponding to the scenario where a service-oriented system architected as a composite service needs to sustain a traffic of requests generated by several users. MOSES integrates within a unified framework different adaptation mechanisms. In this way it achieves greater flexibility in facing various operating environments and the possibly conflicting QoS requirements of several concurrent users. Experimental results obtained with a prototype implementation of MOSES show the effectiveness of the proposed approach.
•Study of the effect of brief-time aging within 650÷850°C on LDSS 2101 SCC resistance.•Thermal aging determined precipitation of chromium carbides and especially nitrides.•LDSS 2101 was susceptible ...to SCC in NACE TM-0177 without/with S2O32− ions.•SCC susceptibility in the presence of S2O32− increased after thermal aging.•Interstitial nitrogen impoverishment negatively affected SCC susceptibility.
In this paper, the effect of brief aging within the 650–850°C temperature range on the resistance of lean duplex stainless steel (LDSS) 2101 to stress corrosion cracking (SCC) was discussed. The thermal aging induced a decrease in Vickers microhardness and an increase in alloy ductility. This behaviour was connected to depletion of interstitial nitrogen in austenite. LDSS 2101 was found to suffer SCC in NACE TM-0177 solution, particularly under specific thermal aging and in the presence of thiosulphate ions (S2O32−) at 10−4 and 10−3M. Crack nucleation and propagation were linked to microstructural variations connected to thermal aging.
Electrochemical Impedance Spectroscopy (EIS) was used to evaluate the inhibitive action of some organic compounds towards the corrosion of a carbon steel, both in a solution simulating the pore ...chemistry of carbonated concrete and in carbonated concrete.
The synthetic solution (SS) has been made by bubbling pure CO
2 in a saturated Ca(OH)
2 solution till obtaining pH 7 and then filtering it. Concrete carbonation has been obtained by maintaining the concrete specimens in CO
2 atmosphere for 80 days, at 68% RH and room temperature.
In SS, benzoate, its amino-derivatives and dicarboxylates were able to form a long-lasting passive layer on the steel surface. Their efficiency improved with time.
In carbonated concrete the additives inducing a decrease in the concrete compressive strength were discarded. Some compounds were monitored for up to 400 days, but only two (the sodium salts of benzoic acid and, particularly, 2-amino benzoic acid) exhibited some inhibitive effect towards the rebar corrosion process.
► Silane conversion coatings as possible alternative to Cr(VI) based pre-treatments. ► 3-mercapto-propyl-trimethoxysilane (PropS-SH) tested on Mg alloys. ► PropS-SH forms a porous conversion coating ...which allows a rapid electrolyte uptake. ► Ce(NO
3)
3 addition to pre-treatment bath improves PropS-SH coating performance. ► Ce
3+ ions presence provides self-healing feature to the coating.
This research investigates the effect of cerium ion addition on the efficiency of a 3-mercapto-propyl-trimethoxysilane (PropS-SH) coating formed on AZ31 magnesium alloy. The coating was obtained by dipping AZ31 coupons in a hydroalcoholic 3-mercapto-propyl-trimethoxysilane solution, added with cerium nitrate, in order to obtain a 5
×
10
−3 or 5
×
10
−4
M Ce
+3 ion concentration. The silane baths were regulated at pH 4 and utilized for filming treatment after 48
h following their preparation. The treated specimens were finally cured for 1
h at 100
°C.
The protective efficiency of cerium modified and unmodified PropS-SH coatings was evaluated by recording potentiodynamic polarization curves and electrochemical impedance spectra in a 0.1
M NaCl environment.
In comparison to PropS-SH coating, cerium nitrate modified silane layer exhibited noticeably improved performances, in particular in presence of a 5
×
10
−3
M Ce
3+ concentration. The increased protectiveness and stability of the modified coatings were attributed to a lower porosity and defectiveness and to self-healing ability provided by Ce
3+ ion presence.
OFHC copper specimens were pre-filmed in hydro-alcoholic solutions of various silanic agents (3-mercapto-propyl-trimethoxy-silane, PropS-SH; bis-triethoxy-silyl-ethane, BTSE;
...n-octadecyl-trimethoxy-silane, OctadecS; phenyl-trimethoxy-silane, PhS) to evaluate the influence of the silane molecule structure towards copper corrosion protection. Linear polarization resistance, potentiodynamic polarization curves, and electrochemical impedance spectroscopy tests were performed in 0.6 M NaCl.
The thiolate bond caused a good anchoring of the silane molecule on the copper surface, which determined a noticeable hindrance to the anodic reaction of copper oxidation. Since this bond was found to be stronger than that of the oxane bond, the PropS-SH coating was more corrosion resistant and more persistent than the other tested silane coatings.
The optimum pre-treatment solution pH was 4, although PropS-SH coating presented some imperfections. At this pH the coating was thicker than that at pH 10, when the silanized layer completely covered the copper surface. Nevertheless, the defects of this layer were so small that they could be plugged, for a prolonged time, by the copper corrosion products.
Modern applications, e.g., for pervasive computing scenarios, are increasingly reliant on systems built from multiple distributed components, which must be suitably composed to meet some specified ...functional and non-functional requirements. A key challenge is how to efficiently and effectively manage such complex systems. The use of self-management capabilities has been suggested as a possible way to address this challenge. To cope with the scalability and robustness issues of large distributed systems, self-management should ideally be architected in a decentralized way, where the overall system behavior emerges from local decisions and interactions. Within this context, we propose GOPRIME, a fully decentralized middleware solution for the adaptive self-assembly of distributed services. The GOPRIME goal is to build and maintain an assembly of services that, besides functional requirements, fulfils also global quality-of-service and structural requirements. The key aspect of GOPRIME is the use of a gossip protocol to achieve decentralized information dissemination and decision making. To show the validity of our approach, we present results from the experimentation of a prototype implementation of GOPRIME in a mobile health application, and an extensive set of simulation experiments that assess the effectiveness of GOPRIME in terms of scalability, robustness and convergence speed.
The formation of stannate and permanganate–phosphate conversion coatings on AZ31 magnesium alloy was investigated
in situ by EIS measurements and their protective performances were studied by ...different electrochemical techniques in diluted (0.05
M) sodium sulphate solution.
The influence that short or long treatment times exert on the performances of such conversion coatings is discussed. While permanganate–phosphate baths always built layers characterized by penetrating cracks, long stannate baths produced layers without interconnected porosity, but were defective. This accounted for the initial greater protectiveness achieved with the stannate treatment; nevertheless, the easy penetration of the electrolytic solution through such a layer quickly decreased its corrosion resistance.
► Inhibitive effect (IE) of two mixtures of organic compounds in carbonated SCP containing 0.1M NaCl was investigated. ► IE of these mixtures in carbonated fly ash and cement mortars partially ...immersed in a solution containing 1% Cl− was studied. ► Inhibitor efficiency was assessed in the solution by polarization curve recording and in the mortars by EIS analysis. ► The mixture of GPH with PhAMB showed the best protective properties in solution. ► The efficiencies were higher in the fly ash mortars than in the cement mortars.
This paper evaluates the inhibitive effect of two mixtures of organic compounds, disodium β-glycerol phosphate (GPH) with sodium 3-aminobenzoate (3AMB) and GPH with sodium N-phenylanthranilate (PhAMB), on the corrosion of carbon steel reinforcement bars embedded in carbonated chloride-polluted ordinary Portland cement (OPC) and alkali-activated fly ash (FA) mortars. Mortar carbonation was achieved by maintaining the specimens in a carbon dioxide (CO2) atmosphere for 60days at room temperature and 65% relative humidity. The OPC and FA mortars were partially immersed in a water solution containing 1% (by binder weight) chlorides (as NaCl), both in the absence and in the presence of the inhibitors.
A carbonated synthetic solution containing 0.1M NaCl simulating the pore chemistry in carbonated chloride-polluted mortars was used to obtain preliminary results on the efficiency of the corrosion inhibitors. Inhibitor efficiency was assessed in the solution by polarization curve recording and in the mortars by electrochemical impedance spectroscopy (EIS) analysis. The mixture of GPH with PhAMB showed the best protective properties.
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