CORROSION MONITORING OF SWCC PLANTS - I:1 Vapor-Side ...

The corrosion monitoring of flash chambers (in the brine flashing zone) and water boxes
in desal unit # 100 and 200 was carried out in lower (4, 6-9), middle (10-12) and last
(19) stages of evaporator and 5-6, 7-8, 9-10 and 11-12 stages of water box. Weight loss
and polarization resistance measurements were used to determine corrosion rates.
Stainless retractable corrosion coupon holders carrying carbon steel or cupronickel
samples were fixed in flash chambers or water boxes for weight loss measurements.
Electro-chemical polarization probes fixed with carbon steel or cupronickel electrodes
were used to measure corrosion rates at regular time intervals. For weight loss
measurements in flash chambers or water boxes, the exposure time varied from 45 days
to 130 days.
Analysis of corrosion data from electrochemical studies and weight loss measurements
indicated that by and large, overall corrosion rates of carbon steel and cupronickel in
flashing brine and water box, respectively, were well within allowable range.
Modification in the present methodology for improving the levels of accuracy and
reliability and its implications on plant operation are discussed.
Vapor Phase Corrosion Monitoring of Al-Khafji MSF Desalination Plant
SWCC Al-Khafji MSF desalination plant was commissioned in 1985. It has a designed
capacity of producing 22727 m 3 /d (5 MIGD). There are 2 desal units (# 100 and # 200),
each unit has 22 stages. The material information and construction particulars for the
evaporator and the water boxes are provided in Table 2. This plant is an additive dosed
plant and in this plant no chemical scavenging of oxygen of make-up is carried out.
Vapor-side corrosion monitoring for this project was carried out in unit # 100 of this
plant.
2. OBJECTIVES
Following are the objectives of the project on Corrosion Monitoring in Al-Khafji
Desalination Plant:
1624