These are areas of different samples of corroded mild steel, one is given a corrosion inhibitor at 40 C and one is given the same inhibitor at 90 C. The EDS results aren't that much different, but the steel at 90 C has more amount of Oxygen than 40 C. From that, and these images, what can I infer in terms of corrosion? Which one is the least corroded, the steel at 40 C or 90 C?
Thank you so much for the kind answers.
Your pictures are too different. Something gone wrong (difference in a temperature should not give such topographical variation for low carbon steel). And for sure you need a control specimen - the one to which no corrosion/inhibitor was applied.
Do you have a tabletop SEM with limited detector choice? If not, get pictures not only in backscattered electrons (as is now), but at secondary electrons also; take pictures at lower accelerating voltage (like 5 kV). Then you can observe surfaces in more detail.
Dear Muhammad,
The worn surface of samples at 90 °C indicated exfoliation on the tribofilm such as island-like. While at 40 °C presented a smoother worn surface, represented by small discontinuous island-like tribofilms. I believe in EDS result for a 40 °C sample will show the highest carbon concentration on the worn surface.
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Dear
calculate the corrosion rate by weight loss method and before going to SEM . do the cross section analyse using EDAX of corroded specimen form this you can able to identify corrosion
Your pictures are too different. Something gone wrong (difference in a temperature should not give such topographical variation for low carbon steel). And for sure you need a control specimen - the one to which no corrosion/inhibitor was applied.
Do you have a tabletop SEM with limited detector choice? If not, get pictures not only in backscattered electrons (as is now), but at secondary electrons also; take pictures at lower accelerating voltage (like 5 kV). Then you can observe surfaces in more detail.
I am not sure but are you taking the two pictures at the same magnification. I agree with Vladimir and use an inhibitor-free sample as a reference sample.
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Dear Muhammad Asep Yudistira, regarding the SEM images to corrosion studies of mild steel for different temperatures 40 and 90 degree shows degradation of the still surface. Operating voltage of the SEM instrument and the materials temperature affects a lot on surface morphology of the sample.And according to micropictures captured at 40 degree is less correded because less degradation of steel is observed than that of the micrographs captured at 90 degree
I disagree. Picture at 40 degrees shows pitting corrosion, possibly around MnS (particles are visible in some pits). Picture at 90 degrees shows flakes, which is not usual for corrosion and may have some other causes.
Dear Mr. Yudistira, corrosion analysis can not be done via just sem pics completely. It usually needs polarization or EIS test, after these tests , sem pics from corrosion place could be helpful for matching the degree of degradation and results of test, but as it is clear in your pics, I think 40C is much corroded and pitting cortosion unlike 90C is obvious.
Dear Muhammad,
TEM micrographs can give the idea of average grain size, contrast of grains, texture, pits, depth of pits or corrosion penetration, also can be calculated by micrographs, can suggest corrosion by drak grain if any, curvature driven expansion, exfoliation depth, large or small scale dissolution etc.
Some highlighted observational conclusion
Your observed photograph depicts some concluded facts and those are:
1. There is a pitting corrosion on first photographs (40 degree centigrade), not on others at 90 degree centigrade. I think here some problem in corrosion interpretation.
2. Depth of pit is small as it seems on the first photographs.
3. Dissolution level in first photograph is high because corrosion rate seems high in first region of photographs.
4. It seems that in photographs 2, there is an elongated grain and hence corrosion rate should be high there at 90 degree centigrade in comparison to 40 degree. It does mean that high dissolution is there on the second photographs at 90 degree centigrade.
5. It also seems there is large crack formation might have occurred on second photographs. However, pitting is higher on first photographs site.
6. On the first photographs some precipitates are visible but not on the second. Can you please take fresh photograph to recheck whether they have more precipitates or not? I think dissolution is high so corroded particle is high on seconds and hence, precipitate size should have little bigger in size compared to first.
7. From first photographs, it shows they have less exfoliation area than second photograph. This is anomaly.
8. There is a small dark grain on first photograph which indicates that local microstructural heterogeneity significantly influences the susceptibility to corrosion.
9. There is no preferred texture on photographs.
10. Each of these additional pits is discrete and isolated from the other pits.
11. Discrete events featuring the localized dissolution of grains
12. Curvature expansion driven is lacking on the surface.
Hope it work out for you.
Ashish
Dear Mohammed Asep Yudistira@
More oxygen means more corrosion products, i guess. The too images do not give enough details.
I agree with Maryam Soleimani@
EIS and polarization tests are useful, in addition to a blank sample. Depending on the nature of the sorption of your inhibitor with the surface when the temperature varies, a thermodynamic study is therefore required.
I think it is very hard by only using SEM as evidence. The EDS element analysis and mapping can provide some more details. The XPS can provide better results.
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