http://www.shimadzu.com/an/industry/petrochemicalchemical/n9j25k00000hxn7g.htm

Simultaneous Analysis of Major and Trace Elements in Plating Solution by ICPE-9820

This report performed simultaneous elemental analysis of the zinc plating solution, from the principle to trace level elements, using the Shimadzu ICPE-9820 multi-type ICP atomic emission spectrometer.

Thank you Shen-Ming.

However, I'm trying to check the coating, not really solution. It is possible to dissolve the coating in an acid and then run ICP. But It still may cause some error and need a lot of attention to not touch the substrate.

Maybe AES, XPS or SIMS would be better options for this concern. However, I want to know if these are common options? and which one is more reliable.

I recommend you line EDX analysis on cross section of sample, eventually then point EDX analysis.

Hi Behzad,

yes your question is an tricky issue. I principle there are several techniques applicable, but my experience showed me that you are on the right way.... See my arguments I experienced in my works I appreciate to share with you:

• as EDX from Jarmila, but you have Fe fluorescence radiation from the steel substrate caused by Zn Ka, so iron content is overestimated, esp for your expected low conc on range smaller 1 wt%. Using low voltage excitation as L radiation could improve this issue, but no experience from me.
• GDOES depth profiling, but HOW to decide when your coating thickness ends?? So you will also get impact of substrate due to bad depth resolution due to sputtering crater and roughness evolution by ion erosion. Same for SNMS technique which is very similar to GDOES, detecting neutrals masses.
• AES, XPS and SIMS are extremely surface sensitive, so you have to deal with other problems like contamination, surface humidity, surface segregations, etc - applying ion sputtering to go into depth brings similar problems as for GDOES and SIMS. Also your high lateral resolution for AES and SIMS will give you problems in terms of homogeneity of your coating and finally these techniques are sensitive for surface roughness. I don't know if that is an issue for your sample, eg small needle-like dendrites, etc?
• an exotic idea from my side: I experienced some elongation or Zn hcp unit cell due to the implementation of iron atoms during electroplating xperiments. Is there a chance to use this effect to evaluate iron content after finding a correlation for that? Usually I his effect is very sensitive. Only an idea.
• So again, we came back to your approach, taking care in stripping the coating from steel substrate using special inhibitors to  inhibit chemical attack of the substrate. So we made some trials about the inhibition behavior, at the end this brought satisfying results for us. But we had Higher Fe content at about 10wt-%, but I fully agree, your task is more severe with content below 1 percent and lower.