GOS was contracted to provide an inspection of the internal corrosion issues relating to the above Cooling Tower System and provide a report. The Inspection was carried out on the 26th September 2017.
Inspection was made by confined space entry into the cooling tower basin and areas accessed by ladder to view upper areas.
Cooling Water Treatment is a science in itself and indeed is the subject of much opinion depending on the commercial aspects of those expressing such opinions. GOS is not supporting any theory on Cooling Tower Water conditioning, or on the other hand denying the virtues of the current system used. GOS is commenting on the corrosion currently experienced which has been caused by a combination of the exposure over time to the changing chemical conditions within the Tower, and the corrosion protection originally provided on the steel structure; – which is by Galvanizing. We do not have any records available that relate to the quality of the Galvanizing or Zinc content, suffice to say that in the passage of time very little Zinc is left on the Steel and Corrosion is all pervading. The Corrosion has occurred an even rate excepting in some local areas where pitting has occurred. Additionally, we have no information on the passivating process that was imposed originally in the startup of the cooling tower which is a protection measure used to pretreat the Zinc prior to service.
Passivation of the Zinc at the outset of operation will enhance its Corrosion Resistance.
The corrosion of Zinc, which initially is described as white metal corrosion occurs when the chemical exposure drifts towards acidic conditions from neutral and likewise towards alkaline conditions up to approximately 8.5 pH; at which point the cargo may be less corrosive towards Zinc. Very dilute concentrations of acids accelerate corrosion rates beyond the limits of usefulness. Alkaline solutions of moderate strength are much less corrosive than corresponding concentrations of acid, but are still corrosive enough to impair the usefulness of zinc.
Location: Singapore
Duration: 2 days.
