Dear Dr. Faysal F. Eliyan,

   Afrer corrosion tests of different conditions such as time or corrosive component, please compare SEM images of inclusions, products and pits around the inclusions resulted from corrosions or EDS analysis results of them. 

   Does this steel contain Ta? Isn't the intensity of the peak labeled as Ta Mb 1.74keV? If so, it may be Si Ka. Inclusions of silicon oxide are often observed in various types of steel. You should pay attention to SiO2, Al2O3, and MnS, which are typical inlusions contained in steel.

According to the X-ray spectra, X-rays emitted from the matrix don't seem to disturb the analysis of the inclusion. If X-rays emitted from sample matrix disturb analyses of inclusions or precipiates, please consider using a grazing exit X-ray analysis shown in the attached file. 

I would be happy if my information clould be helpful for your research.

Sincerely,

Tohru Awane

Fukuoka, Japan

I think the protocol followed in polymer degradation studies may help you.

What kind of steel is this?

Dear Dr. Faysal F. Eliyan,

   Afrer corrosion tests of different conditions such as time or corrosive component, please compare SEM images of inclusions, products and pits around the inclusions resulted from corrosions or EDS analysis results of them. 

   Does this steel contain Ta? Isn't the intensity of the peak labeled as Ta Mb 1.74keV? If so, it may be Si Ka. Inclusions of silicon oxide are often observed in various types of steel. You should pay attention to SiO2, Al2O3, and MnS, which are typical inlusions contained in steel.

According to the X-ray spectra, X-rays emitted from the matrix don't seem to disturb the analysis of the inclusion. If X-rays emitted from sample matrix disturb analyses of inclusions or precipiates, please consider using a grazing exit X-ray analysis shown in the attached file. 

I would be happy if my information clould be helpful for your research.

Sincerely,

Tohru Awane

Fukuoka, Japan

Dear Faysal,

electrochemical impedance spectroscopy (EIS), the scanning vibrating electrode technique (SVET) and the scanning ion-selective electrode technique (SIET) are used for studying corrosion process in a small area. EIS is usually aided by SVET or localized impedance spectroscopy (LEIS).

Regards,

Alicja

Hi Alicja,

I'm curious, have you used before SVET for a similar system?

Thanks,

Faysal

Hi Faysal,

this equipment is used to study the protective coatings' ability to self-repair. The electric field is generated in a plane above the electrochemically active surface, so the local electrochemical activity of the coating can be recorded and quantified in real time. In my opinion SVET or LEIS can be useful also in your application, because you observe local corrosion processes. You also have the electrochemically active surface.

Cheers,

Alicja

Dear Faysal

I would like to give information the corrosion process. As we know corrosion may be defined simply as the reaction of a metal with its environment that produces some changes at the surface or near surface of the metal.  For example, the corrosion products caused by CO2 are FeCO3, Fe3C  on the surface of steel. We can study  in terms of degradation of metal, especially at the microstructural level, in order to develop protection measures against corrosion. The profile product on the steel can be observed by some methods, i.e SEM/EDS for microstructural characterisation of corrosion product material, grazing incidence XRD/AXA/Syncrotron radiation diffraction(GISRD).

Sincerely,

Simon Sembiring

Hi Mirosław, it is X65 pipeline steel.

Thanks

Hi Alicja,

Sounds interesting, I am studying ultra small, problematic inclusions, on the scale of tens of micrometers. I'm limited by the resolution the probe, which can't go less than 50 micros. I either need to upgrade the instrument or synthesize bigger inclusions.

Faysal 

Hi Faysal,

I attach specifications of one of SVET models. Such equipment is used with success to scan a surface of coatings containing nano- and microcapsules. These capsules contain corrosion inhibitors. After coating damage a corrosion inhibitor reacts with coating's matrix. One can see cathodic and anodic areas on coating's surface. At the beginning corrosion process is observed. Then, when a corrosion inhibitor starts reacting, electrochemically active areas disappear. Everything happens on very small surface, according to capsule size and can be study using SVET.

Alicja

If your concern is the impact of non-metallic inclusions on corrosion, you should not be interested by the corrosion behavior of non-metallic inclusions, because even if they are the cause of the corrosion of the steel, they don't corrode. They cause corrosion because non-metallic inclusions are more cathodic than the steel, therefore it is the steel around them that corrodes. To control the corrosion of the steel, you need to control the amount of inclusions in the steel. For instance, in the aircraft industry because of the impact of these inclusions on fatigue and corrosion, the steel specifications define the cleanliness of the material. If you buy a steel ,the supplier should guarantee that it contains very few and small inclusions.

Thanks Nihad,

Basically we do expect that for inclusions containing both alumina and MnS the corrosion will intensify AROUND them - as you said. We want to determine the galvanic effects to be linked to a clear corrosion mechanism.

Thanks for your input,

Your concern should be the presence of MnS that trap the hydrogen resulting from the corrosion reaction of the steel in the pipeline environment. If the steel is not high-strength you are OK, otherwise the issue is cracking induced by hydrogen that happens along MnS stringers.

As to determine the impact of non-metallic inclusions on the corrosion of steels, I would suggest that you choose specimens that would be free from inclusions (need some cuts) and others with inclusions. You can polish the surface and look at it in the microscope, the non-metallic inclusions are fairly observed on a non-etched surface. Then you can do both polarization curves and OCP (open circuit potential) in a solution that mimics the pipeline environment on the two types of specimens. By comparison you'll be able to determine the impact of non-metallic inclusions (dimension, quantity) on the corrosion behavior of the steel. The observation of the specimens after the tests will give you an indication on what happened during the tests. Thus you'll be able to determine if it is the same phenomena that is oberved in the pipeline steels in real conditions....This could be a good student project!...:-)

I see, basically we're now introducing synthetic inclusions inside electrolytic iron, to be molten collectively together and recast in specimens having different types of inclusions of different sizes/compositions. It is sort of a comparative study that more systematically looks at the effects of the inclusions in a one corrosive environment!

Hum...Would you be able to mimic the strength and residual stresses of the "real" steel? This is very important for the corrosion behavior... The stress-state of the interface between the inclusions and the matrix should have a big impact...