This paper gives an assessment of a series of studies aimed at establishing the corrosion potentials prevalent in working deaerator systems of small 20-40 MW peat fired steam raising units. Two Ag/AgCl reference electrodes were inserted into each deaerator and their tips positioned at different feedwater storage vessel weld run locations. As well as corrosion potential, water chemistry parameters, unit load and feedwater temperature details were recorded.It was shown that the reference electrodes: (i) sensibly recorded the corrosion potential in deaerator feedwater storage vessel weldments, (ii) the level of corrosion potential was similar at different weld locations, (iii) the agreement between both readings in any vessel was excellent, and (iv) exhibited a range in durability with the 0 1 m reference electrode being better than the 3 0 m.An initial potential hysteresis, where corrosion potential (CP) values remained at higher levels than those predicted from potential-dissolved oxygen trends, was consistently observed in all three deaerators. Also, various sudden changes in corrosion potential were recorded and it was shown that these coincided with either normal working unit load fluctuations or off-load events. A significant influence of surface condition was evidenced, in that a bright clean weld surface recorded a CP value which was consistently over 150 mV more positive than that shown by an oxidised weld surface.Finally, it was concluded that the present deaerator system corrosion potential data compared well with other reported potential-dissolved oxygen trends and exhibited reasonable agreement with modern day empirical and deterministic models which predicted crack growth behaviour in stainless and low alloy steels in hot aqueous environments.