With reference to the above thread Inconel 625 has superior external corrosion resistance in marine environment compared to Inconel 825. Hence Inconel 625 does not require painting compared to Inconel 825 which does require.
825 is a high alloy stainless steel. It is more designed for elevated temp service than for corrosion resistance. A 6%Mo superaustenitic stainless (such as AL-6XN) will have much better pitting resistance.
In fact in aqueous chloride environments I would pick a 6% Mo alloy over 625.
If you really want better corrosion resistance move to a C alloy (C22, 686, 59), they are the same price as 625 and have far better pitting resistance.