Engineering and Technology Journal

The coupling effect of coating and inhibition has been investigated in the present work. polypyrrole coating with adding coumarin was applied on carbon steel to protect it against corrosion. Electropolymerization process by cyclic voltammeter was carried out in 0.2M oxalic acid electrolyte containing 0.1M pyrrole monomer without and with 0.01M coumarin as an eco-friendly inhibitor. SEM/EDS, AFM and FTIR techniques were used to identify the coating film. Corrosion test using Potentiostat was achieved for uncoated and coated specimens and the results indicated that the corrosion potentials became nobler compared with uncoated specimen, this means that the anodic sites were covered by undoped and doped PPy film as illustrated from the deceasing of anodic and cathodic Tafel slopes. Protection efficiencies were acceptable and good (71.46% for PPy film and 77.47% for coumarin/PPy film). The polarization resistance was increased from 0.114 Ω.cm2 for uncoated C.S. to 0.176 and 0.404 Ω.cm2 for PPy coated and coumarin/PPy coated C.S. While the porosity percentage was 0.44% and 4.50 for PPy coated and coumarin/PPy coated C.S. due to increasing the roughness of coumarin/PPy film.

In the present work, corrosion inhibition of Mild steel in 1M H2SO4 solution by Rosmarinus Officinalis Leaves extract was studied by weight loss and potentiostatic methods. Increasing acid concentration leads to an increase in the corrosion rate of the electrode. The variable conditions used in this investigation are (100 to 1000 ppm at 25oC. Rosmarinus Officinalis Leaves extract for Mild steel. It has been found that the concentrates as a compelling consumption inhibitor for gentle steel in acidic medium. The hindrance process is credited to the development of an adsorbed film of inhibitor on the metal surface, which secures the metal against corrosion. The inhibition efficiency was observed that increase with increasing inhibitor concentration up to maximum 92% for 1000 ppm at 25 oC. The results show that the corrosion rate without inhibitor is 5.6 mpy while with inhibitor be 0.43 mpy, that is mean the corrosion rate was improved more than 90%. The effects of immersion time (2 h) at 25oC on the inhibition of corrosion have also been improved corrosion resistance. The results obtained show that Rosmarinus Officinalis Leaves Extract could serve as an excellent friendly green corrosion inhibitor. FTIR results indicate that this herb containing different chemical bonds (C-C, CH2, C-O-C, Cellulose) with steel surface producing barrier layer to protect the surface

It is known that corrosion inhibitors and coatings are the best choices to use in oil refinery; therefore, we suggested using both inhibitors and coating to get more efficiency for corrosion control. Polypyrrole coating (PPy) without and with doping by anodic inhibitors were investigated to protect the tank from corrosion in light naphtha unit at Al-Dura refinery. Polypyrrole coating was deposited as nanofibers by electropolymerization using cyclic voltammetry method. Doped polypyrrole coating was applied by adding anodic inhibitor represented by chromate, phosphate and molybdate in acidic electrolyte. The coated layers were examined by SEM/EDS, FTIR and AFM. These examinations showed that coating layers were as nanofibers on carbon steel surface with average roughness in nanoscale as follow: 24.2 nm for PO4≡/PPy, 108 nm for PPy, 122 nm for B4O7=/PPy and 139 nm for MoO4=/PPy coating. Corrosion measurements were investigated by Potentiostat in oil medium at 60oC which represent the average temperature of light naphtha unit; the results showed that the highest protection efficiency was 78.34% in the presence of PO4≡/PPy coating and the others were 77.85% for PPy, 72.64% for B4O7=/PPy and 68.83% for MoO4=/PPy coating. The presence of inhibitor within the structure of polypyrrole coating leads to repairing the defects that may be produced by corrosion process and then the protection will take a long time to be destroyed. The protection by inhibitor doped PPy suggesting reduce the ionic conductivity of coating film especially in the presence of phosphate anions, where the porosity percents was 0.00025 for PO4≡/PPy compared with other coatings (0.04794 for PPy, 0.00043 for B4O7=/PPy, and 0.13083 for MoO4=/PPy).

External corrosion by soil’s components is a serious problem in many steel structures such as pipelines and tanks, thus many methods are applied to reduce this risk. Nanotechnology almost gives improving for conventional protection methods.
Investigation on nano Al2O3 doped polypyrrole coating has been done on carbon steel structures to protect them in two simulated soil environments include (0.01M NaCl + 0.01M NaHCO3) and (0.01M NaCl + 0.01M Na2SO4). Electropolymerization of pyrrole monomer carried out in oxalic acid with suspended nano alumina using cyclic voltammogram method. Characterization of produced film was done by SEM/EDS and the results indicated the uniformly distribution of coating in the presence of nano alumina confirming the presence of Al2O3 NPs by EDS analysis. Also FTIR spectra showed the occurred incorporation between polypyrole and nanoalumina in deposited film on steel surface.
The presence of nano alumina behaves as repaired to healing the defects in polymer film by chemical, mechanical and electrochemical factors and then gives long life time for service; this result was concluded through the improving in protection efficiency of Al2O3 NPs/PPy film compared with conventional red paint which is uses to protect carbon steel structures.

Corrosion processes are accountable for serious losses in the oil industry. Although organic and inorganic materials and mixed materials inhibitors have been used for a long time to control or reduce corrosion. Using nano-materials as inhibitors has gained an increasing applications role because of their exceptional properties. Nano materials are good corrosion inhibitors because they possess many advantages such as high efficiency of inhibition, low cost, minimum toxicity and effortless production. This work examines the use of nano-materials as inhibitors to prevent corrosion of carbon steel in drilling mud. Anti-corrosion properties of zinc and nickel ferrite nano materials (ZnFe2O4, Zn0.6Ni0.4Fe2O4) have been investigated over carbon steel in local Iraqi bentonite mud as a source of the corrosion. It has been found that under the given conditions, ferrites act as efficient corrosion inhibitors of carbon steel.

Pomegranate shells were investigated as green inhibitors for steel 44-2 in 0.1M HCl at various temperatures (30, 40, 50, and 60) °C using electrochemical technique. Five concentrations of inhibitor were added 4, 8, 12, and 16 ppm. Corrosion tests were performed by Potentiostat at 5 mV.sec-1 scan rate and the data measured by Tafel extrapolation method such as Tafel slopes, corrosion current density and corrosion potential. Inhibition efficiencies were calculated and indicated that 8 ppm was the best concentration for inhibition especially at 60oC, where was 96.47%. Pomegranate Shells behaves as anodic inhibitor type and obeys Langmuir adsorption isotherm. The equilibrium constant of the adsorption-desorption process and the apparent free energy of adsorption confirm the physicsorption of Pomegranate shells. FTIR spectroscopy was used to test film formed on steel surface compared with FTIR spectrum of Pomegranate Shells. These spectra confirm the formation of Fe2+Pomegranate shells complex.

In this work, three nanoparticles were applied as coatings on carbon steel using atomization method (cold spraying) by airbrush.The coatings includednano Al2O3,nanoSiC and nanoZrO2 materials. The characterization of coated surfaces has been investigated by AFM and SEM. All these inspections indicated that the deposition of nanoparticles on carbon steel surface was uniform and homogeneous. Thethickness of coated layers was calculated using gravimetric method, while the particle size and roughness were measured from the analysis of atomic force microscopy.With constant conditions of coating, nano alumina coating gave the highest thickness (6.2216 nm) due to agglomeration of these particles compared with others as illustrated in SEM images. Corrosion test was performed to estimate the corrosion resistance, protection efficiency and porosity percentage which indicated the role of nano particle coating on corrosion control. These data showed that the nano alumina was better than other coatings and gave PE 99.69%.
Cyclic polarization was also estimated to show the probability of pitting corrosion. The coating with alumina gave the best data for decreasing the chance of pitting corrosion.

This research involves study corrosion of low carbon steel under static and flow
conditions at 200L/h in the absence and presence of CO2 at two rates 9 and 30 ml/min
at four temperatures by electrochemical method using potentiostat. Numerical model
was achieved to compare between the experimental and theoretical results to estimate
corrosion rate. The results show that the presence of CO2 under static conditions
shifts the Ecorr toward noble direction, while under flow condition the presence of CO2
shift Ecorr toward active or noble direction at two rates of gas. The data of corrosion
rate in mm/y indicate that the presence of CO2 with two flow rate increased the rate
compared with the case of absence of CO2 under static conditions except one case,
while under flow conditions, the presence of 9 ml/min. CO2 increases the corrosion
rate, while the presence of 30 ml/min. CO2 decreases the rate because of formation
FeCO3 scale except at 298K. A Mathematical model was done which show the
volumetric flow rate of CO2 and finally the corrosion rate of CO2 correlated with
dimensionless groups and independent parameters.

This paper presents the influence of carbon steel microstructure on the corrosion rates. Four types of microstructures have obtained by quenching and tempering and iso-thermal annealing. These microstructures are:
banded ferrite/pearlite microstructure, fine ferrite/pearlite microstructure, coarse ferrite/pearlite microstructure and tempered martensite microstructure.
General corrosion and localized corrosion (penetration rates) were determined via mass loss and optical microscopy. The different microstructures of steels investigated in this paper revealed corrosion rate variations of 0.8– 3.2 mm y-1 and 3.3–6.4 - mm y-1 for the general and localized forms, respectively. The corrosion stability of the various microstructures may arise from variations of phases within the steel. A banded ferrite/pearlite microstructures have worse general corrosion properties, while tempered martensite worse microstructures have localized pitting corrosion properties. Coarse ferrite/pearlite microstructures have better localized pitting corrosion resistances compared to others investigated microstructures This paper has demonstrated that, microstructure is an important consideration when selecting carbon steel for an industrial corrosion resistance application.

The corrosion in petroleum pipelines was investigated by the studying the corrosion of carbon steel in crude oil and refined petroleum products which include gasoline, kerosene, and gas oil. Weight loss method was used in which test specimens of carbon steel, with a known weights, were immersed in the test media for a total exposure time of 60 days. The weight loss was measured at an interval of 10 days and the corrosion rate was determined. The results showed that corrosion rate are highest for gasoline followed by kerosene, gas oil and crude oil, in a decreasing order. The observed pattern in the corrosion behavior is consistent with the density and weight percent of hydrogen in the hydrocarbon products. The corrosion rate increases with decreasing density and increasing weight percent of hydrogen. Experiments were carried out at different temperatures (30, 60, 90 and 120oC) at a constant partial pressure of CO2 (50psi) in 3.5% NaCl solution. The results indicated that as partial pressure of CO2 and temperature increase, corrosion rate increases due to due to continuous dissolution of iron ion and formation of weak carbonic acid. The weak carbonic acid dissociates into carbonate and hydrogen ion, which increases the cathodic reaction on the metal surface.The presence of small amount of H2S (0.4 ppm) increases the corrosion rate significantly.

The main objective of this study was to evaluate the microbiologically
influenced corrosion of carbon steel in water, samples of water taken from Al-Hilla rivers and distill water (control medium ). Corrosion analyses by using (Liner polarization tafel test; weight loss method ; microstructure examination , surface roughness test and X-Ray diffraction analysis) and microbiological analyses by using
(Isolation and identification by using appearance factors microscopic ,culturing factors and biochemical tests for biofilm of corrosion product) are used in this study. The result of corrosion analyses shows the corrosion rates of carbon steel in rivers water are more than that in control water, the microstructure examination and surface roughness tests show increase in roughness of met.al. surfaces which are
under the corrosion medium (rivers water) compared with control medium. The result of microbiological analyses shows the slides that made from the biofilm (product of corrosion) under microscopic appear small bacilli negative gram strain (G-ve) bacteria, where as culturing test shows small colonies with 2.5ìm in diameter of bacteria have mucin appearance and green pigments as well as the result from
biochemical tests; these facts indicate that Pseudomonas aeruginosa bacteria are correlated with the type of corrosion occurring in the carbon steel in the rivers water.

The aim of present work is to study the effect of different heat treatments [full annealing ,normalizing ,and hardening and tempering at (300C° ,600C°)] on general corrosion and erosion-corrosion for a carbon steel type (C35) in 3.5wt% NaCl solution as corrosive medium for general corrosion while in erosion-corrosion ,slurry with 1wt% SiO2 sand was added to 3.5wt% NaCl solution as the erodent. The experimental work tests were done using special device which was designed and manufactured according to (G73 ASTM) using traditional weight loss technique to measure weight loss rate or corrosion rate in (gmd) unit.
It was found that the general corrosion rates for all heat treated specimens were lower than erosion-corrosion rate. The erosion-corrosion rate of specimen which was quenched and tempered at 600C° was found smaller than other heat treated specimens The normalizing heat treatment of low carbon steel improves the general pure corrosion resistance after immersion 20 day in 3.5 wt% NaCl solution.

An experimental work was performed to study the effect of Zn, Cu ions on
the corrosion rate of carbon steel in distilled and tap water solution containing, 25
& 50 ppm concentration of Zn, Cu ions at pH range 4, 6 &8 in distilled water and
at pH8 in tap water at room temperature under both static for 10 weeks and 1, 2,
6 &12 hours with dynamic conditions. The obtained results showed that the
corrosion rate was increased in the presence of 50 ppm of Cu ions in tap water
(2.326 mpy) after 10 weeks, under static conditions, whereas under dynamic
conditions, it was reached (10.511 mpy), the presence of fine suspended solid
particles in the solutions may also cause an increase in corrosion rate due to their
movement over the carbon steel surface .In contrast, the presence Zn ions in
solution as sacrificial anode, therefore, the corrosion rate was 2.24 times less than
that in presence of Cu ions, at the same conditions. In distilled water, the
corrosion rates were decreasing slightly with adding Zinc and copper ions
comparing to absence of metals ions in solution except at pH4 in the presence
50ppm of Cu ions may be accounted due to the increasing in the conductivity of
the solution, under static conditions. At 25ppm of Zn ions lowering in corrosion
rate may be explained that the Zn ions were protected carbon steel surface by
sacrificial. In the absence of Zn, Cu ions were also carried out.

In present work, The corrosion behavior of carbon steel in sodium chloride (NaCl)
solution with different concentrations was studied .Effects of mixing speed (0 to 2220) r.p.m
and the solution temperature (25, 35, 45, 55, 65)0c on cathodic protection current density were
studied, that would provide a full cathodic protection for tube metal specimen of carbon steel
immersed in 3.5% NaCl solution by sacrificial anode method using magnesium (Mg) as
sacrificial anode.
The results show that the concentration of sodium chloride in the electrolyte is an
important factor in determining corrosion rate, 3.5 % concentration of sodium chloride gives
maximum rate of corrosion. In addition, it has been found that the cathodic protection current
density showed sharp increasing with mixing speed. The results have showed also that the
cathodic protection current density increased with increasing the solution temperature and
shifts the protection potential to high negative value.

The inhibition of the oxygen reduction reaction on a carbon steel rotating
cylinder electrode in naturally aerated 600 ppm Cl- solution was studied using an
optimum inhibitor blend, i.e., Sodium Nitrite (SN): Sodium Hexametaphosphate
(SHMP) = 500:100 obtained via a weight loss technique. Potentiostatic technique, then,
was applied at different bulk temperatures and various flow rates using un-inhibited and
inhibited solutions under isothermal and controlled conditions of heat transfer.
In an un-inhibited solution and under isothermal conditions, with limiting conditions of
concentration polarization, the limiting current density of oxygen reduction reaction is
flow and temperature dependent. The charge transfer of the oxygen reduction reaction is
a 4 electron process in the range of bulk temperature employed from 303 to 323 K.
Under heat transfer conditions, the charge transfer is still 4 electron process up to 336 K
interfacial temperature, above which the contribution of the 2 electron process appeared.
Moreover, the limiting current density values of the oxygen reduction reaction in
inhibited solutions is much lower than those under identical conditions in un-inhibited
solutions. This confirms the inhibition of the cathodic reaction, i.e., the oxygen
reduction reaction under isothermal and heat transfer conditions, due to SHMP.