How we can determine the satisfaction of chemical cleaning (Acid wash) of SS pipe line?

[adeliry]

We want to start chemical washing of lube oil pipelines. before starting acid treatment we will do degreasing and water flushing, but I want to know if we start to acid treatment, which tests must be done to determine that treatment is complete?
If we measure total Iron and Fe2+ and Fe3+ ions, which one indicate that the source is dissolved rusts and which one is from piping corrosion?( we will use inhibitor also).

If there is any complete procedures that include laboratory tests for chemical cleaning ( both alkali and acid wash), will be very useful for me.

Thanks,

adeliry@gmail.com