Experimental Study: Corrosion and Erosion of Stainless Steel Alloys

This project investigates the corrosion and erosion behavior of stainless steel alloys under both static and flow-induced conditions. The methodology involves the determination of breakdown potential and passive film chemistry in static environments, utilizing alloys like UNS S32304 and UNS S3...Read More

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Methodology
The focus of this particular research work is to extend the idea as well as the knowledge on the
topic of corrosion as well as corrosion erosion on the stainless steel in flow induced as well as
static environment. As a result several methods have been adopted to assist the project achieves
its aim that had been set for the study. In the case of the static corrosion conditions, there was
determination of the breakdown potential of at least six alloys. The passive film chemistry of the
stainless chemistry was determined after the exposure to the environment at the open circuit
potential. The alloys of the stainless steel which were used for the case if the study included
UNSS32304 as well as UNS S32101(Roy et al 2018). These two particular alloys were chosen
because of the variation in the content of the variation in the content of the manganese and the
close pitting resistant which is equivalent to stated number (PREVN)
Figure 1: SLM Machine(Zhang et al 2017)
Under the conditions of the flow-induced corrosion, there was consideration of at least four
alloys. The Erosion –corrosion behaviour of such alloys were too studied in the submerged
impinging jet rig commonly known as SIJ in the condition of the saturated CO2 as well as
aerated air for about 15m/s velocity The results were then produced on a simulation platform of
FEA analysis that will be shred later in the this particular figure. From the chosen alloy samples

of the stainless steels, UNSS30403 as well as UNS32101 were produced from the SLM 125 HL
machine which is actually equipped with a 200w YLR–Fuser –Laser (λ=1070 nm) whose
location is in the first floor of the CADET building The produced sample specimen for the
experiments had dimensions of 10x10x10 mm3 . There was use of the higher velocity of about
24m/s in the study of erosion-corrosion behaviour of the samples under saturated solution of
Sodium Chloride(NaCl) commonly called brine(Wu et al 2016).
Selected Stainless steel for the study
There was use of at least six different samples of the stainless steel in the static corrosion
evaluation at the start of the experiment. These samples included UNS S30403, UNS S32304,
and UNS S31603), 316LSS in the case of the duplex stainless steel while the standard samples
included the use of the UNS S32205. The selection of the four alloys was very important
considering their representation of at least and every class of the alloys. Two grades of the
stainless steel(Duplex) were chosen because of the research interest on these particular alloys)

Sample of the steel used (Zhang et al 2017)
Alloys used for research work were as indicated in the figure below

Concentrated Sodium Chloride used for the experiment
This is also called brine
The experiment considered the use of two samples of the brine in the research work.3.5% of the
solution of NaCl was aerated to be used. Also the oilfield brine which is usually saturated with
large quantities of carbon dioxide gas was used. The adopted oilfield brine had the following
characteristics
Table 1: Brine properties(Zhang et al 2015)
Experimental Methods
All the samples of the stainless steel were cut into the flat plates which were basically 3mm thick
into section which were square 10mmx10mm. There was soldering of wire to one face of every
specimen before they could be mounted into the epoxy resin. These specimen were ground to

finish of from 240 down to 4000 grit by the use of the SiC paper, washed with the distilled water
before they could be left to dry I the hot air
Flow-Induced Corrosion Experimental Methods
Determination of the Pure Erosion and Corrosion
A rig used in the jet impingement that has re-circulating system was actually adopted for the
system. A mixture of fluid and sand was passed through the arrangement of two nozzles with the
diameter of 4mm. The distance of 5mm was set to be as at an angle of 90 degrees as the jet
impinges on to the surface of the samples.
Figure Standoff distance

Figure 2: submerged impinging Jet Rig commonly known as SIJ rig(Zhang et al. 2015).
There was use of the electro chemical methods alongside analysis of the weight loss in order to
completely isolate the possible contribution due to the erosion as well as corrosion. There was
evaluation of the anodic polarization tests to assist in the measurements of the changes in the
corrosion rate under the conditions of the impingement .Also in evaluation were cathodic as well
as anodic polarization tests as carried out in coupons. Feeding the values generated to achieve
FEA results was the most crucial part of this work. The samples below were obtained after
simulation.
Calibration of the Submerged Impinging Jet Ring
The condition of any experiment carried in the laboratory should be recurrence for it to be
tolerated. This has however brought challenges since it is not easy to reproduce the conditions.
Consistent calibration of the research tools for this study was done to put into consideration the

regular changes in the conditions of operation. Calibration of the frequency of the pump for
example in submerged impinging jet ring is to indicate the fluid or particles velocity leaving
through the nozzle. In case sand is also included, no uniformity would be obtained in mixing
sand in the reservoir. There is possibility that sand may be deceived in the pipe. In the
calibrations, matters like collision of the particles with one another and action of sweeping of the
liquid jet should also be put into consideration. Reports have shown that the added particles of
sand to the reservoir does not all impact the sample surface.
Calibrations for velocity
The centrifugal pump powered by electric motor regulated by self-frequency provides the
necessary power for driving the impingement action(Roy and Edwards 2018). Data of the fluid
flowing out of the pump is used in the analysis of the average velocity of the fluid that streams
out from the nozzle. Provided that the diameter of the nozzle and the frequency of the pump are
both known, calculation can therefore be done to determine the rate of flow of the fluid through
the nozzle(Ramírez et al 2017). This can be obtained through collecting a specific volume of the
fluid coming out of the nozzle at intervals of time. Frequencies of different values can be applied
where the computation of the rates of flow is determined. By use of the surface area of the nozzle
through which the liquid exits, the velocity can be determined from the rate of flow in the
nozzle(Schütze et al 2016).
Calibration for the concentration of sand
The ratios of weights of particles of sand to that of the solution in the reservoir is what is termed
as sand concentration. As was clarified, the exact concentration of sand coming out of the nozzle
is not the same as the amount which was initially in the reservoir(Sriyono et al 2016). A

specified amount of slurry at the exit of the nozzle is taken for the determination of the exact
concentration of sand leaving the nozzle. Filtration is done to separate the particles from the
liquid solution and then the particles are dried and weighed. The analysis gives a specified
amount of sand that comes out of the nozzle.
Equipment for Surface Analysis for the research
Scanning Electron Microscope (SEM)
Scanning Electron Microscope uses pressure variation and a range of resolution between 3 nm
and 20 nm for electron microscopy.
Figure showing Evo MA Series Scanning Electron Microscope
SEM gave a total magnification of between 1-7 million with an accelerating voltage of 20 kV at
a distance between 9-10 mm.
Focused Ion Beam (FIB)
FIB was used in the preparation of Transmission Electron Microscope sample. Focused Ion
Beam which is more accurate was installed within Field Emission Gan Scanning Electron

Microscope of high resolution to differentiate the acquisition of images between Transmission
Electron Microscope (TEM) and the Focused Ion Beam (FIB). FIB uses focused beams of ions
as opposed to the use of beam of electrons in SEM. On striking the surface of the sample,
materials of less quantity are sputtered by the beam of ion exits from the surface as neutral atoms
or secondary ions(Suresh, Mudali, and Raj 2019). Secondary electrons also result from the
primary beams(Raja et al 2016). The image is then formed from the collection of signals of the
secondary electrons of the ions sputtered resulting from the primary beam that raters on the
surface of the simple.
Diagram of a Focused Ion Beam
Figure 4: Diagram of a Focused Ion Beam(Zhang et al 2015)
Transmission Electron Microscopy

Transmission Electron Microscope was used to obtain quality contrasts by applying bright field
and dark field techniques of imaging.
Expected Outcome
One of the examples of the cyclic polarization curves as produced by the use of the one
sample(UNS S32101) in the case of aerated 3.5% NaCl as well as oil filed environment CO2
saturated .The determination of the breakdown potential as the case where the density of current
is attained at a value of 10 μA/cm2 . It is expected that the breakdown of all the alloys will be as
indicated in the figure below. The results are likely to indicate that the breakdown is more in the
case of the carbon dioxide saturated sample as opposed to the 3.5% NaCl for the tested
alloys(Abualigaledari 2018).

Figure 6: Simulation results of the localized samples
Figure 7: Graphical analysis(Awad, Asker and Hatton 2018).

The other observations made included the following:
The values of the open circuit of the sample asymptotically ennobled with the time exposure.
However after the activation at value of 0.85V, the value was found to be more positive in 3.5%
NaCl than in the case of the CO2-saturated oilfield. The potentials of all the alloys were found to
be more positive for both CO2-saturated oilfield and 3.5% NaCl after an exposure of
24hours(Awad, Asker and Hatton 2018)
In the case of the 3.5% NaCl aerated, there was more negativity with the sample of UNS
S32101.The 24 hour exposure of the sample of UNS S32101 produced more anodic ennobled
results in the aerated environment.
Limitations of this technique
The results that are produced are concentrated on the specific/localized points. This makes it
extremely hard for the comprehensive conclusion to be made in regard to the variable under
investigation(Popoola 2019).
Advantages
The simulation of the process allows for the detection of the possible areas of error for the
purposes of the correction before the necessary measures can be used(Muthukumar 2017). This
increase safety measures when the component is finally subjected to the actual or the practical
applications.

Secondly the method has involved application of the extreme conditions of the operation. This
implies that any other sort of the application that will fall below the evaluated as well as stated
values will definitely give a perfect result(Ford et al 2015).

REFERNECES
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for Oil and Gas Transmission Pipeline (Doctoral dissertation, North Dakota State University).
Awad, T.S., Asker, D. and Hatton, B.D., 2018. Food-safe modification of stainless steel food-
processing surfaces to reduce bacterial biofilms. ACS applied materials & interfaces, 10(27),
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Ford, F.P., Scott, P.M., Combrade, P. and Amzallag, C., 2015. Environmentally-Assisted
Degradation of Structural Materials in Water Cooled Nuclear Reactors–An Introduction.
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