Corrosion and Dye

The corrosion resistance of trivalent chrome conversion coatings on electroplated zinc is studied and compared with that of hexavalent chrome conversion coatings in salt spray testing conditions. The trivalent chrome conversion coatings and hexavalent chrome conversion coatings were unstable at pH 3. All samples had more than 5 % of the surface area covered with white rust after 24 hours of salt fog exposure. The corrosion resistance of the samples is as follows: TM 3108 ~ SP 25 > 747 at pH 6.5. The highest resistance obtained on the TM 3108 with white rust appeared after 400 hours of salt fog exposure. All of the hexavalent chrome conversion coatings and trivalent chrome conversion coatings had corrosion current densities (1.26×10-7 ÷ 1.82×10-7 A/cm2) much smaller than corrosion current density of the zinc electrodeposited sample (7.7×10-6 A/cm2). The compositions of corrosion products of sample surfaces after exposure were investigated. The results of analysis by means of X-ray diffraction showed that the corrosion products formed on zinc coatings, trivalent and hexavalent CCCs in atmospheric conditions of Hanoi had the distinctions specialty of the humid tropical climates. Zinc sulfate hydroxide hydrate Zn4SO4(OH)6.H2O; Zinc carbonate hydroxide hydrate Zn4CO3(OH)6.H2O; Simonkolleite Zn5(OH)8Cl2.H2O; Chromium Sulfate Cr2(SO4)3; Zinc chloride sulfate hydroxide hydrat Zn12(OH)15(SO4)3Cl3.H2O; Eskolaite Cr2O3 had been identified. The presence of SO2 resulted in the formation of Zinc sulfate hydroxide hydrate Zn4SO4(OH)6.H2O. After 5 years of exposure in atmospheric conditions, the hexavalent CCCs on zinc coatings had show the best corrosion resistance and the least corrosion products. The corrosion resistance of the samples decreased in the order: 747 > SP25 ~ TM 3108 > Zn.

The corrosion inhibition of tin by Phyllanthus niruri extract in different solutions of HCl (1N, 2N, 3N) and H2SO4 (1N, 2N, 3N) was investigated by weight loss and thermometric methods at 301K temperature. From the study it was found that the inhibition efficiency increases with the increase in the concentration of extract in HCl and H2SO4 solutions. Results indicate that Phyllanthus niruri extract was an efficient natural corrosion inhibitor in acidic media. The stem extract of the Phyllanthus niruri is better than leave extract of the plant. Absorption of Phyllanthus niruri depends on its chemical compositions which showed the presence of various compounds like alkaloids, flavanoids, steroids, tannins etc. which has O, N and S atoms with lone pair electrons to form co-ordinate bonding with metal.

The corrosion inhibition efficacy of alcoholic extract of stem, leaves and fruits of plant Tribulus Terrestris for mild steel in H2SO4 has been studied in relation to the concentration of inhibitor and temperature by mass loss method. Inhibition efficiency increases with inhibitor concentration but decreases with increase of temperature. The thermodynamic parameters revealed that the inhibition of corrosion is due to adsorption of the inhibitor on the metal surface. The negative free energy values shows spontaneity of the adsorption process with the assumption of Langmuir adsorption isotherm.

The use of inhibitors for the control of corrosion of metals which are in contact with aggressive environment is an accepted practice. It is needless to point out the importance of cheap, safe inhibitors of corrosion. Plant extracts have become important as an environmentally acceptable, readily available and renewable source for wide range of inhibitors. The inhibition of the corrosion of copper in nitric acid solutions by senesio extract has been studied using chemical and electrochemical techniques. Inhibition was found to increase with increasing concentration of the senesio extract. Senesio extract is a rich source of ingredients which have very high inhibition efficiency. The adsorption of senesio extract on copper surface was found to obey Langmuir adsorption isotherm. The polarization data revealed that senesio extract acts as mixed type inhibitors. The surface morphology was analyzed.

Corrosion on SS-304 in brackish environment. Any compound capable of donating free chlorine ions (Cl -) to an aqueous (water-based) solution has the potential for causing failure in stainless steels. The chlorine ion is extremely electronegative, therefore very reactive with certain compounds and elements. This reactivity is part of its usefulness in certain situations, but becomes a double-edged sword where stainless steel is concerned. Experimental corrosion studies on commercial SS - 304 have been carried out. The experiments were carried in brackish environment with a concentration variation, pH variation and contact time variation. The experiments were carried out by weight loss method, gasometry study and open circuit polarization studies. The post corrosion sample’s micro structures were analyzed with the aid of EDS (Energy dispersive spectroscopy) equipped SEM (Scanning Electron Microscope) EDS (Energy dispersive spectroscopy) instrument to detect the morphology of corrosion by-products. For further verification x-ray diffraction method was also used to detect any possible emerging corrosion by products on the sample’s surface. Experimental results confirmed that SS-304immersed in brackish environment with a variation of concentration , experience very little corrosion. EDS study and x-ray diffraction results indicate that the possible ensuing corrosion by products are Iron oxides, chrome oxides, iron chloride and nickel hydride oxide

Corrosion inhibition of mild steel in 1 M HCl solutions by methanol extracts of Costus lucanusianus was investigated at concentrations of 0.1 g/L, 0.2 g/L, 0.5 g/L, 0.7 g/L and 1 g/L using thermo-gravimetric analysis from 303 K – 333 K. Maximum inhibition efficiency of 88% and 86% for mild steel and aluminium was observed. The adsorption was found to obey Fruendlich isotherm. GC-MS analysis showed major components of Methanol Stem Extract (MSE) and Methanol leave Extract (MLE) as 1,3-bis (3-bromophenyl) 1,3-propanedione (12.60%) and 3–hydroxyl-4-methoxy benzylalcohol (72.17%) respectively. Quantum chemical calculations using Density Functional Theory employing the Becke exchange functional and the Lee Yang Parr correlation functional (BLYP), together with the generalized gradient approximation (GGA) employing the “double numeric polarization” (DNP) basis sets was used in optimization of the geometries of the molecules. The inhibitors showed significant inhibitive effect following the trend MSE > MLE.

This paper predicted the corrosion rates of three refinery boiler components namely: Baffle wall tubes, vapourizing tube bank and the superheater coils, using a mathematical model developed from the balance equation of the refinery boiler. The results obtained were then compared those already measured by Ultrasonic Thickness Scanning Technique (UTS). The essence is to determine if the prediction equation can be useful in predicting the life expectancy of the various boiler components. The prediction was done for a period of four years. Metal loss recorded for Baffle Wall Tubes was 0.10 mm to 1.10 mm from UTS, while the one from the model was 0.11 mm to 0.98 mm. Metal loss recorded for vapourizing tube bank was 0.06 mm to 1.00 mm from UTS and that from the model was 0.05 mm to 0.98 mm. Metal loss recorded for superheater coil was 0.026 mm to 0.67 mm. The percentage deviation calculated between the model and that from UTS showed a correlation between the rates observed by the different measurement tools. The introduction of the inhibitor model indicated that inhibitor application can greatly reduce the corrosion rates of the refinery boiler’s components. The paper has also shown that the mathematical predictive model can be used to predict the corrosion rates of the internal boiler components as compared to the recorded readings of the Ultrasonic Thickness Scanning Technique.

Corrosion is a natural process which converts a refined metal in to a more chemically stable from. It is the gradual destruction of material by chemical of electrochemical reaction with their environment. It can be prevented if the metal is coated with something which does not allow moisture and oxygen to react with it. It can be controlled by either sacrificial protection or by antirust solution. The naturally occurring plant product are ecofriendly, compatible, non polluting, less toxic, easily available, biodegradable so can widely be use without side effect. Tylophora indica has been selected for the study to it’s corrosion inhibition efficiency. It is easily available in any season. It is also called annatmul. It is endemic to southern and eastern part of india. Is it used for the treatment of jaundice, inflammation ,dermatitis and rheumatism. It contains septicine, isatylocrebrinsterol,wax,tylophorinicine.Corrosion inhibition efficiency of leaves of Tylophora indica was studied for aluminium in HCl solution. Maximum inhibition efficiency was found 70.50% in 0.5 N HCl an 0.7% inhibitor for concentration. Inhibition efficiency was studied in three different acid like- HCl,H2SO4 ,HNO3 in four different concentrations like [0.5N,1N,1.5N,2N] with different concentrations of inhibitors [0.1,0.3,0.5,0.7] Weight loss method and thermometric method were used. Inhibition efficiency was found to be increase in concentration of inhibitor and decrease with increase in acid strength

Annatto extract was investigated as a cheap and ecologically friendly alternative corrosion inhibitor. The corrosion process was monitored with mild steel coupons in 1.0 M hydrochloric acid at temperatures between 30oC to 90oC by weight loss and spectroscopic techniques. The extract effectively inhibited the corrosion of mild steel in the acid at temperatures studied. Inhibition efficiency obtained varied with temperature and extract concentration. Adsorption models were used to predict the nature of the extract-steel surface interaction. Thermodynamic models provide evidence of spontaneous physical and chemical adsorption mechanism with the evolution of heat. Kinetic studies reveal deepening effect on the activation potential well in the presence of the extract. The effects of solvent and synergistic intensifiers on the effectiveness of the dye extract were also assessed. Heavy metal ion composition in the formulation was within acceptable limit of environmental and health safety.

Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. The most common kinds of corrosion result from electrochemical reactions. It can be prevented if the metal is coated with something which does not allow moisture and oxygen to react with it. It can be controlled by either alloying or by anti rust solutions. The naturally occurring plant products are eco-friendly, compatible, nonpolluting, less toxic, easily available, biodegradable and economic to be used as corrosion inhibitor.Euphorbia caducifolia has been selected to study its corrosion inhibition efficiency. It is easily available in any season. It is native to Thar Desert of India and located on rocky terrain, hills. It is used for treatment of bleeding wound, cutaneous eruption, urinary problems, kidney stones, rheumatic pain, bronchitis, jaundice, diabities, stomach pain, hernia etc. It is also called “Thor” and “Danda-thor”. It contains caudicifolin) norcycloartane type triterpene, cyclocaducinol, triterpenes euphol, tirucallol and cycloartenol. Corrosion inhibition efficiency of arial parts of Euphorbia caducifolia was studied for aluminium in HNO3. Maximum inhibition efficiency was found 92.17% in 1N HNO3 acid with 0.8% leaf corrosion inhibitor whereas it was 90.53% for stem and 89.94% for flower with same concentration of inhibitor i.e. 0.8%. Inhibition efficiency was studied in different concentration of acid (1N, 1.5N, 2N and 2.5N) with different concentration of inhibitor (0.2%, 0.4%, 0.6% and 0.8%). Weight loss and thermometric methods were used. Inhibition efficiency was found to be increase with increase in concentration of inhibitor and decrease with increase in acid strength.