environmental sulfur test (as per std ionic mixture in RH chamber)  
might be, pulp and paper industry grade of computer control system   
might have some lesson to learn paper back in mid 90s.  it is all in  
the design, you need to keep majority of the stuff away, and dealt  
with what ever left of few.... if you are talking about oil and gas  
industry, that is different stuff all together... in conclusion, you  
need to deal with it at system level,not assembly or sub-assembly  
level... based on a coating to block sulfur ingress is risky the  
least...
imo.
    jk
On Jul 30, 2014, at 12:47 PM, Paul Jackson wrote:

> We have a customer whose PCBAs are subjected to flower of sulfur  
> rich environments. The sulfur quickly corrodes any area not covered  
> in soldermask. They would like to use a conformal coating but their  
> research to-date has only come up with one solution which has  
> published data specifically concerning sulfur and the coating is  
> too viscous for their application.
>
> Does anyone have experience with a conformal coating which is  
> proven to survive in an environment with sulfur?
>
> Any help would be greatly appreciated.
>
> Thanks,
>
> Paul
> Omni Circuit Boards
>
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