You know that the measurement of carbon is not only very challanging, unreliable and but needs a lot of optimism in believing the data? I mean, if you would try to analyse carbin by WDS, I would take this problem of mounting seriously into account but for EDS measurements? Have you ever simulated a carbide signal which countains e.g. 25% of C? Did you realized the comparatively tiny intensity in comparison to the Fe signal? And you hopefully know how big is a) noise, and b) manufacturer-specific corrections of the EDS signal at low energy?

I don't want claim that I am the expert for analysing carbon but I would not recommend to do it. This is one reason why software packages inplemented a deconvolution of C from data since C you will have practically always caused by contamination. And I only hope that not carbon is your element of interest but carbides, since in steel usually clearly less than 1% C is in solution. This you won't see by EDS (whatever you perhaps see and interprete as C signal). 

 please contact Dr .Anwar Ul-Hamid . he can answer you

It is possible to measure and quantify the carbon content in different phases of steel via SEM and EDX but not in a standard SEM. I have made demo mesurements in an UHV-SEM of dual phase steel containing 0.2wt% C. I could see the different phases ferrite and martensite and their different carbon contents. But it is challenging. The cross section sample was broken out of the epoxy and carefully cleaned via ultrasonic cleaning in tetrahydrofuran, isopropanol and ethanol each time for 2x15 minutes. One should also clean the sample holder. You can try it this way.

If you can not remove the resin you can maybe cover the surface before putting it into the resin. Sometimes we use electrodeposition of nickel or copper if these elements are not present in the sample.

Other preparation ideas are focused ion beam (FIB) or cross section ion polishing. You have to be careful with argon ions. They overlap with your carbon signal. For mounting your sample you can also use silver glue. After one day it is not outgasing any more. But never use carbon tape.

Other analysis techniques for measuring carbon in steel are secondary ion mass spectromety (SIMS) and atom probe. If you are looking for higher carbon amounts then you can use Auger electron spectroscopy (AES). I have successfully used it to map the carbites in steel or to show the distribution of the carbon in corrosion products on a zinc layer on top of the steel for example in hydrozincite.

Good luck with your measurements.

Dear all

I really appreciate all your comments and suggestions.

I apologize for not making myself clear in my question. I am not interested in the carbon present in the steel but the carbon present in my corrosion product, specially when the steel (e.g. API 5L X65) is exposed to CO2 corrosion. FeCO3 is commonly found on the steel surface (depending on temperature, pH, etc). It is also common to see a porous layer of Fe3C enriched with alloying elements. Currently I am using epoxy to mount my samples (after being exposed to CO2 corrosion) for cross section analysis. I use EDS for chemical composition along the thickness of the corrosion product and as you can see C is one of my elements of interest.

Thanks again for all your suggestions.

Fernando

As i know, it is the best way for cross section analysis. Maybe you can take metal spraying on the sample with something cover the steel.

Hi,

I fully agree with Mr Nolze about difficulties and challenges to measure carbon in a quantitative way. It not easy to achieve reliable results.

So I would suggest to use original surface without any preparation step to analyse your corrosion layer. I assume your preparation will bring in more problems regarding your original carbon load in your layer than it brings you forward in your task. Pls think about this idea.

And As next step pls decide whether it is necessary to detect carbon directly or to detect your corrosion phases formed, eg the carbon containing phases overall?  This is another approach forward, but I am not sure if it makes sense I in your case. So an elemental depth profiling technique could bring a solution or eg. Raman Spectroscopy for the corrosion products...is another idea from my side.

I don't think EDS is the b St way to measure the C%. Why don't you try using Leco analysis? It's fast and accurate! 

One way of circumventing the problem is to use a source with known Carbon content. Then doing measurements on your specimen and the reference specimen under the same conditions - same WD, same filament current, same acceleration voltage etc. ie mounting the 2 specimens at the same time This can give some reliable results ( though not fully accurate !)

You can use hot conductive copper mounting.

Parameters of hot mounting (Temp.= 180oC, Pressure= 4200 psi)

 I agree with  Subhojit Chakraborty, EDS is not good enough to measure C content. A little C contaminate can result in the change of peak intensity.  Maybe WDS is OK.

Dear all

Thank you very much for all your comments and suggestions.

XRD only get crystal structure, you can not know C content.  Besides, XRD sport is not a small point.