Surfactants as Inhibitors for Alkaline Corrosion of Aluminium

Inhibition of aluminium corrosion in NaOH solution by anionic surfactant as sodium (lauryl)sulphate, cationic surfactant as cetyl trimethyl ammonium bromide and non ionic surfactant asTriton-X 100 has been studied using weight-loss and hydrogen evolution methods. It is foundthat the inhibition efficiency depends on the type of SAS as well as its concentration. The orderof increasing inhibition is as followsSLS < Triton - X 100 < CTABThermodynamic parameters are calculated.

Corrosion of two kinds of cast steels containing chromium in hot concentrated alkaline

A typical hot concentrated alkaline corrosion environment exists in alumina metallurgical industry, so that steel materials with outstanding alkaline corrosion resistance are strongly demanded for its processing equipment. In this paper, the corrosion resistance of two kinds of martensitic cast steels containing chromium in static 303g/L NaOH alkaline solution at 85℃ was studied through polarization and potential-time curves, corrosion weight loss and corrosion morphology analysis. Experimental results showed that protection effect by passive film of cast steel containing Cr was temporary. The low carbon steel without Cr content also exhibited chemical passivity in the same solution. The corrosion mode of the tested Cr-containing cast steel was composed of active dissolving corrosion and caustic embrittlement cracking. Dissolving corrosion was the primary mechanism for the induced weight loss, while severe caustic embrittlement cracking was secondary. With the increase of chromium content in the cast steel, the tendency of the caustic embrittlement cracking decreased, while the active dissolving corrosion increased.

KINETIC FACTORS AFFECTING THE CORROSION OF SiO_2 IN SILICATE GLASSES CAUSED BY ALKALINE SOLUTIONS

The corrosion of a ZrO2 containing alkali re-sistant silicate glass, float glass and silica glass caused by the aqueous solution of NaOH was studied by use of correlation method with spectrophotometry. Effects of the corroding tem-perature, time and solution concentration on the rate of reac-tion and the degree of corrosion were investigated; effects of the apparent activation energy and the experimental value of frequency factor on the rate constant were discussed.

Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Potentiodynamic polarization tests and slow strain rate test（SSRT） in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking（SCC） behavior of 7003 aluminum alloy（AA7003） in acid and alkaline chloride solutions under various applied potentials（Ea）. The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution（AD） at open-circuit potential（OCP） and is highly susceptible to hydrogen embrittlement（HE） at high negative Ea in the solutions with p H levels of 4 and 11. The susceptibility increases with negative shift in the potential when Ea is less than-1000 m V vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when Ea is equal to-1000 m V vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.

Microstructure modification and corrosion resistance enhancement of die-cast Mg-Al-Re alloy by Sr alloying

The effects of Sr additions on the microstructure and corrosion performance of a Mg-Al-RE alloy in 3.5 wt.%Na Cl saturated with Mg(OH)_(2) have been investigated.Microstructure examination reveals that the Sr addition introduces additional intermetallic phases,refines intermetallic networks and dendritic grains,and improves the network continuity.More Al and rare earth elements can be identified in the intermetallics and grain boundaries or inter-dendrite regions under a transmission electron microscope and secondary electron microscope,respectively.On the Sr-containing intermetallic phases and the refined microstructure,the oxide films become more protective,resulting in more corrosion resistant boundary areas and thus dendrite grain grooves.Hence,the presence of large amounts of intermetallics and boundaries can enhance the corrosion performance of the Mg-Al-RE alloy containing Sr.

Effect of yttrium on corrosion behavior of extruded AZ61 Mg alloy

The corrosion behavior of extruded AZ61 magnesium alloy with different addition of yttrium ranging from 0 to 0.9 wt.%was investigated.The electrochemical techniques in naturally-aerated 0.01 M NaCl solution and the surface analyses are utilized.The electrochemical results show that the pitting potential,time to pitting initiation,film and charge transfer resistances of the AZ61 specimens increased with the increase of yttrium content.Surface analyses indicate that yttrium promotes the formation of passive films and the refinement of the precipitates and matrix grains.

Double-layer Modifi cation of Water-based Aluminum with SiO2 and Polyacrylic Acid by Solgel Process and in situ Polymerization

A double-layer aluminum consisting of an aluminum core and a shellof SiO2 and polyacrylic acid was synthesized.This modified aluminum was used to improve the corrosion resistance and dispersive property of aluminum in waterborne media.TEM,FTIR,XPS,and EDX determination showed that PAA and SiO2 were coated on the surface of aluminum.Evolved hydrogen detection showed that the corrosion resistance of composite particle had been markedly improved.Maximum corrosion inhibition efficiency of SiO2 coated aluminum（SiO2@Al）was 95.1% while that of double-layer coated aluminum（PAA/SiO2@Al）was 98.8%.Meanwhile,polyacrylic acid layer improved the agglomeration of aluminum significantly.According to the dispersibility test,the particle size of 50% volume fraction [d（0.5）] of aluminum,SiO2@Aland PAA/SiO2@Alwere 42,53,and 34 μm,respectively.

Corrosion Inhibition of SiCp/5A06 Aluminum Metal Matrix Composite by Cerium Conversion Treatment

This article studies the effects of the CeCl3 concentrations in conversion solutions with and without addition of NaCl, pH-values of conversion solution, drying temperature, time and temperature of immersion on the Ce-conversion coatings for corrosion protection of the SiCp/5A06 Al-MMC and 5A06 Al-alloy in the 3.5% NaCl aqueous solution at room temperature. Potentiodynamic polarization tests reveal that the Ce-conversion treatment could markedly improve the pitting corrosion resistance of the composite and the matrix alloy in chloride containing environment. The best corrosion resistance effects are obtained for the samples treatment in 1% CeCl3.7H2O/3.5% NaCl solution at 45℃ for 60 min, followed by drying at 100 ℃ for 30 min. Examinations by means of scanning electron microscopy （SEM）, energy dispersion spectroscopy （EDS） and X-ray photoelectron spectroscopy （XPS） indicate that this behavior is due to the precipitation of Ce-oxides/hydroxides on the cathodic intermetallics and the Al-oxide film on the rest of the metal matrix.

Corrosion behavior of Ti_(3)AlC_(2) in molten KOH at 700℃

This paper investigated the corrosion behaviors of Ti_(3)AlC_(2) at 700℃in molten KOH with various mass ratios.If the mass ratio of KOH:Ti_(3)AlC_(2)≤2,Ti_(3)AlC_(2) can resist KOH hot corrosion in 2 h.Ti_(3)AlC_(2) suffered serious corrosion attack if the mass ratio≥3.The main compositions of corroded samples were amorphous graphite and potassium titanates(K_(2)O·nTiO_(2)).If the samples were washed by acid and dried,potassium titanates could decompose to K_(2)O and amorphous rutile.Based on the experimental results,a corrosion mechanism of Ti_(3)AlC_(2) in molten KOH was proposed.

Stability Mechanism of Laser-induced Fluorinated Super-hydrophobic Coating in Alkaline Solution

Great attention has been focused on super-hydrophobic surfaces due to their fantastic applications.Fluoride chemicals are widely used to fabricate super-hydrophobic surfaces due to their convenience,simplicity,and high efficiency.Previous research has made extensively efforts on corrosion resistance of fluorinated super-hydrophobic surfaces in corrosive media.Nevertheless,rare papers focused on the underlying reasons of anticorrosion property and stability mechanism on the fluorinated super-hydrophobic coatings in alkaline solution.Therefore,this work aims to reveal these mechanisms of fluorinated super-hydrophobic copper samples in strong alkaline solution(pH 13).Through the characterization of surface wettability and surface morphology,the laser-induced super-hydrophobic surface retained excellent stability after soaking in alkaline solution for 4 h.Through measurement of chemical compositions,the anticorrosion mechanism and stability mechanism of the fluorinated super-hydrophobic surface were proposed.Importantly,the hydroxyl ion(OH−)can further promote the hydrolysis reaction to improve the density and bonding strength of the fluoride molecules.Finally,the electrochemical experiments(PDP and EIS tests)were conducted to validate the rationality of our proposed conclusions.