Protection of stainless steel by polyaniline films against corrosion in aqueous environments

Polyaniline (PANI) thin films were electrochemically deposited by cyclic voltammetry on stainless steel electrode previously covered by a thin film of polyvinyl acetate (PVAc). The corrosion resistance of PANI covered stainless steel substrates was estimated by using potentiodynamic polarization curves and its linear polarization resistance (LPR) was measured in 0.5 M H₂SO₄, 0.5 M NaCl and 0.5 M NaOH aqueous solutions at room temperature. The results indicate that the PANI-PVAc films did improve the corrosion resistance of the stainless steel in NaOH, behaving even worst, in the case of PANI film, than the uncoated substrate. In H₂SO₄ both PANI and PANI-PVAc coatings gave good protection for the stainless steel electrode, with a slightly better performance of PANI-PVAc than PANI. In NaCl solution both PANI and PANI-PVAc films provided a good protection against corrosion. The better performance of PANI-PVAc coatings for corrosion protection in basic media may be due to its major chemical stability compared to simple PANI films, which lose their conductivity in high pH solutions. The E _corr (free corrosion potential) value of the coated substrate was in the passive region of the uncoated substrate in acidic environment but in the active region in neutral or basic environment.     

Land-use classification in central Spain using SIR-A and MSS imagery

Abstract

Methods for making more efficient use of synthetic aperture radar (SAR) imagery are considered. Local standard deviation and autocorrelation texture measures are used to provide information on the spatial variability in the scattering cross-section. Use of these statistics in a window of 180×180m improved classification success rates from 39 to 66 per cent with digitized shuttle imaging radar (S1R-A) data. Multispectral scanner (MSS) achieves 70 per cent success with the same window size and, by combining this with SAR, a 78 per cent success rate is reached.     

Probability density fittings of corrosion test-data: Implications on C6H15NO3 effectiveness on concrete steel-rebar corrosion

In this study, corrosion test-data of steel-rebar in concrete were subjected to the fittings of the Normal, Gumbel and the Weibull probability distribution functions. This was done to investigate the suitability of the results of the fitted test-data, by these distributions, for modelling the effectiveness of C₆H₁₅NO₃, triethanolamine (TEA), admixtures on the corrosion of steel-rebar in concrete in NaCl and in H₂SO₄ test-media. For this, six different concentrations of TEA were admixed in replicates of steel-reinforced concrete samples which were immersed in the saline/marine and the microbial/industrial simulating test-environments for seventy-five days. From these, distribution fittings of the non-destructive electrochemical measurements were subjected to the Kolmogorov–Smirnov goodness-of-fit statistics and to the analyses of variance modelling for studying test-data compatibility to the fittings and testing significance. Although all fittings of test-data followed similar trends of significant testing, the fittings of the corrosion rate test data followed the Weibull more than the Normal and the Gumbel distribution fittings, thus supporting use of the Weibull fittings for modelling effectiveness. The effectiveness models on rebar corrosion, based on these, identified 0.083% TEA with optimal inhibition efficiency, η = 72.17± 10.68%, in NaCl medium while 0.667% TEA was the only admixture with positive effectiveness, η = 56.45±15.85%, in H₂SO₄ medium. These results bear implications on the concentrations of TEA for effective corrosion protection of concrete steel-rebar in saline/marine and in industrial/microbial environments.     

A quantitative inherent reconfiguration theory for a class of systems†

In aircraft flight control, most control surfaces are in pairs (elevators, ailerons, canards etc.), with each pair normally controlled as a single unit. If a surface fails, the usual approach is to attempt explicit identification and switch-in of compensation prepared for that contingency. In this paper each surface is separately controlled, permitting ‘inherent reconfiguration’, wherein the design is a priori made such that despite one or several simultaneous surface failures, the system still satisfies the original performance tolerance (of course over a smaller dynamic range), with the same original fixed compensation. Inherent reconfiguration is a natural extension of quantitative feedback theory (QFT), wherein the system design is tuned to the plant uncertainty set 𝒫 ={P}, and to the acceptable system output set,. In QFT one designs a priori so that the system output is in  for all P in 𝒫 Surface failures simply enlarge the set 𝒫. The transparency of QFT enables the designer to readily see the extra ‘cost of feedback’ for this enlargement of & by inclusion of surface failures.     

THERMAL RESISTANCE OF BACILLUS CEREUS SPORES AS AFFECTED BY ADDITIVES IN THE RECOVERY MEDIUM

The effects of the addition of starch, glucose, sodium chloride, sodium citrate, monopotassium phosphate and disodium phosphate to the recovery medium on apparent heat resistance of Bacillus cereus spores (ATCC 4342, 7004 and 9818) were investigated. Sodium citrate, monopotassium and disodium phosphate at concentrations of 0.1% were effective inhibitory agents for heat injured B. cereus spores especially for strain 9818, although only monopotassium and disodium phosphate caused a significant reduction (p < 0.05) in D-values obtained for strain 9818. Sodium chloride also had a marked effect on the recovery of heat injured spores. Concentration as low as 0.5% caused a significant reduction in the recovery rates for strains 9818 and 7004. In all cases, increasing the salt levels from 0.5 to 4% resulted in a progressive decrease in spore recovery. D-values gradually decreased as the salt content increased, although the concentrations which produced statistically significant differences (p < 0.05) varied among strains. The addition of starch at 0.1% resulted in a significant increase in the counts for strains 9818 and 7004. In contrast, glucose (0.1%), did not significantly modify the counts obtained Neither of these compounds affected decimal reduction times. No statistical significance (p>0.05) differences were detected among z-values for the spores of the three strains recovered in the presence of different additives assayed. z-Values ranged from 6.67 to 8.32, with a mean value of 7.56 ± 0.46C .