Hi Amina,

The SEM/EDS quantification of light elements is problematic. This is because of the large variations in absorption effects in the low energy range, as well as the variations in background calculation due to high absorption edges and high statistical errors. Quantification for light elements is difficult even with using ultrathin window or windowless X-ray detectors because of the severe self-absorption of low energy X-rays, poor detection efficiency, and low fluorescence yield.

Most SEM-EDS systems use beam energy of 20 keV because it is a good compromise between the requirements of obtaining adequate overvoltage and minimizing absorption in the specimen. However, such high beam energy will penetrate deep into the steel substrate and may mask the X-rays of light elements that produce energies below 2 keV. Therefore, if your have been using high accelerating voltage, I suggest you try to use a low voltage (≤10 kV) to reduce the x-rays generated from the steel substrate. EDS measurements of light elements and many 3d transition elements can still be accomplished at accelerating voltage as low as 1.5 kV, see E. D. Boyes, Adv. Mat. 1998, 10, 1277.

On another topic, have you tried using FTIR spectroscopy in analysing the bacterial induced corrosion on the steel samples? FTIR is much simpler technique and is more suitable for studying organic substances. You may find the attached paper useful.

Hope this helps,

Kind regards

Mr Ameer K Ibraheem , thank you very much for your informative answer;

only, I really want to help me interpreting the EDS spectrum obtained because I have already done the surface analyzes of my coupons and the results are there and this while waiting to see the possibility of doing the surface analyzes by FTIR spectroscopy as you advised me; ;

Best reguards.

Hi Amina,

I don't know the purpose of your work, how you prepared your samples and whether you have applied specific bacteria on them. It will be difficult to distinguish between ordinary rust that is caused by exposure to water for example and that that is caused by bacteria without further information. I suggest that you examine the steel coupons with an optical microscope to try to see what signs of corrosion you have on the coupons. However, I have commented on the EDS spectrums on the power point file and messaged it to you. I hope you find the comments useful.

Kind regards