The Inhibited Effect of Cysteine Towards the Corrosion of Copper in Nitric Acid Solution
The detailed study of cysteine (Cys) as corrosion inhibitor for copper in nitric acid solution has been performed through weight loss, electrochemical polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) measurements. The effect of inhibitor concentration, temperature and immersion time against inhibitor action was investigated. Results show that Cys may be used as an efficient inhibitor for copper in nitric acid at higher temperatures (98% at 50°C). Potentiodynamic polarization studies reveal that Cysteine acts as a mixed-type inhibitor without any change in the mechanism of hydrogen evolution. The adsorption of this compound on copper surface obeys Langmuir's adsorption isotherm and has a chemisorptions mechanism.
Double Layer Capacitance of Iron and Corrosion Inhibition with Polymethylene Diamines
The effect of α,ω‐polymethylenediamines on the corrosion of iron in deaerated was investigated by polarization measurements and colorimetric analysis of solution. The adsorption of these inhibitors at the metal/solution interface was monitored by measurement of the double layer capacitance using the single pulse method. 1,3‐propanediamine was found to be a better inhibitor than ethylenediamine, but no further improvement in per cent inhibition resulted upon increasing the chain length from . Increased inhibitor efficiency for hydrocarbon chains longer than eight carbon atoms was attributed to the concomitant decreased solubility. On a relative solubility basis, the C6‐diamine was more efficient than the C12‐diamine, although both inhibitors produced 90% inhibition at a reduced concentration of 0.1. The double layer capacitance was approximately constant at 21 µF/cm2 for the C2‐ through C8‐diamines, and alternated between 6 and 14 µF/cm2 for the C9‐ through C12‐diamines. The constancy at 21 µF/cm2 suggets that diamines with up to 8 carbon atoms are adsorbed in the same configuration, probably the flat position. The subsequent reduction and alternation in capacitance is believed due to a structuring of the adsorbate similar to that in the bulk where certain physical properties oscillate with carbon number. Colorimetric analysis of solutions with and without additions showed the dissolution rates to be higher than those measured by the polarization technique, possibly due to the "chunk" effect, in which dislodged grains of metal contribute to the total but not faradaic corrosion.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.