Page 186 - CW E-Magazine (3-12-2024)

Special Report

Fig. 11: 3 Shutdown schemes (A,B,C) indicating corrosion rate.
therefore is the best out of the three
sequences shown in the figure(12, 13).

Cell room
The cell-room environment is very
corrosive because of the presence of
brine, caustic, and wet chlorine, and
hence the structural steel is generally
protected against exposure to these
corrodents. Following the preparation
of the surface of the steel to a near-white
metal state, it is coated first with 0.05-
0.075 mm of organic zinc or polyamide
epoxy primer and then with 0.13 mm
of catalysed polyamide or amine-cured
paint. The siding and roofing materials
are generally FRP or vinyl ester panels.

Walkways are fabricated with FRP
grating. All concrete surfaces in the cell
room are constructed with fusion-bonded
epoxy coated steel reinforcing bars, Fig. 12: Crevice corrosion of titanium plate of a brine heat exchanger.
and Type V Portland cement (sulphate thick, three-component silica or surface with their seams welded and
resisting & low tri-calcium aluminate glass fabric-reinforced bisphenol, an spark tested, to protect floors, equip-
cement), providing a minimum com- epoxy, using an aromatic amine catalyst ment pads, trenches, etc.
pressive strength of 30,000 kPa and curing system. A 3-mm thick PVC, PP,
sloped at 2%. Cell pedestals, equipment and PE thermoplastic sheet stocks are The materials of construction in-
supports, floors, and trenches, formed the latest materials, which are attached the cell renewal area are the same as
of concrete, are covered with 3-6 mm to concrete structures as a permanent those used in the cell room. Corrosion

186 Chemical Weekly December 3, 2024

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