chlor alkali coatings

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CHLOR-ALKALI COATINGS

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REFURBISHMENT SERVICES

By Dr Derek C Armstrong

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KEY FACTS

INEOS manufactures all its own coatings

All INEOS coatings can be tailored to customers membrane cycles

Anodes – 8, 10, 12 years

Cathodes – 8, 10, 12, 15, 16 years

INEOS coatings are currently installed in the following electrolysers

• INEOS

• UHDE

• AK

• MGC

INEOS HAS BEEN MANUFACTURING CHLOR ALKALI ELECTRODES FOR 118 YEARS

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INEOS ANODE COATINGS

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Anode Coatings

� A layer of conductive, catalytic material applied to the surface of a titanium anode to promote chlorine evolution at low voltage

� Applied in layers followed by stoving (thermal decomposition)

� Key components are RuO2, IrO2

� Voltage performance dependent on

surface area

� Surface shows a ‘cracked’ structure

� Lost by 2 mechanisms

� Mechanical loss

� Alkaline wear

SEM of INEOS anode coating 1.5K magnification

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Anode Coatings – Features to consider in Coating Selection

Feature What is it? Impact ?

Over-potential Additional voltage generated by the surface resistance of the coating

Higher over potentials mean higher power consumption- adds to operating cost

Alkali Wear Resistance

Resistance to loss of Ruthenium, the critical catalytic element, during operation

High alkali wear = short anode life, or more expensive anodes as suppliers add more RuO2

High Chlorate in brine

ClO3- is produced as a by

product of Cl2 productionPotentially environmentally damaging and discharge may be limited

Higher chemical usage in chlorate destruction system

Higher rates of corrosion in caustic evaporators as higher levels of chlorate in caustic soda.

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INEOS Anode Coating – LOW CHLORINE OVER POTENTIAL

INEOS ANODE coatings have been designed to provide a chlorine over-

voltage of 20-30mV lower than typical commercial coatings. This represents a

1% power saving for customers (eg based on $80 per MWh a 100kte plant

would save $120k/year)

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0 1 2 3 4 5 6 7 8

chlorine over-voltage (mV)

Time

Chlorine over-voltage

INEOS ANODE COATING

TYPICAL COMMERCIAL ANODE COATING

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INEOS Anode Coating – LOW ALKALINE WEAR

Accelerated Alkaline Wear Test - Voltage Rise - 20kA/m2 Current Density

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1

2

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Duration (Hours)

Voltage ( V )

CP304 CompetitorINEOS

INEOS ANODE coatings have been designed to provide significantly superior alkaline

wear performance over other commercially available chlor-alkali anode coatings.

With the move to zero gap where the membrane lies directly up against the membrane

good alkaline wear resistance in very important for coating life as the surface of the

membrane is alkaline.

Time

StandardCommercialcoating

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INEOS Anode Coating – LOW CHLORATE IN BRINE

INEOS Competitor

Chlorate (g/l) 0.05 0.3

Hypochlorite (g/l) 0.8 1.5

INEOS ANODE coatings have been designed to provide a very low level of

chlorate (and hypochlorite) in brine.

This translates to less chemical usage for chlorate destruction but more

importantly lower chlorate in caustic, stopping evaporator corrosion.

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INEOS CATHODE COATINGS

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Cathode Coatings

� A layer of conductive, catalytic material applied to the surface of a cathode to promote hydrogen evolution at low voltage.

� Key components are many and vary dependent upon the supplier.

e.g. RuO2, Raney nickel, Pt group metal oxides, Nickel Oxides, sulfides, carbides.

� Applied using a range of techniques depending upon the coating type.

e.g. “spray-bake”, electro deposition, plasma spray, electroless plating, catholyte additive.

� Total coating thickness 200microns to

>1 micron depending upon type.

� Best have a high ratio of catalytic area

to apparent area.

� Loss mechanisms are� Wear

� Reverse current dissolution

� poisoning

SEM of INEOS cathode coating – 4K magnification

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Typical Progression of Cathode Coating Wear

• Non-precious metal coatings normally last 4-8 years

• INEOS precious metal coating shows virtually no loss (warrantied for 16 years)

• >18 years experience in our FM mono-polar technology

• 13 years experience on BICHLOR™ with no measurable loss

Cathode coating loading vs time on load - schematic

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100

0

time on load

% of starting catalyst remaining in

coating

Non-precious metal coating

INEOS precious metal coating

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The INEOS CATHODE Coating has an exceptionally high resistance to

reverse currents making it the ideal cathode coating for all zero gap

electrolysers.

Coating totally failed

-0.350

-0.300

-0.250

-0.200

-0.150

-0.100

-0.050

0.000

0 100 200 300 400 500 600 700 800

E(V) verus RHE

Test Cycles

Accelerated Cathode Durability Data85°C 32% NaOH (Data HF Resistance Corrected)

INEOS cathode coating Competitor cathode coating

High resistance to reverse currents

Non precious metal cathode coating

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Features of INEOS Cathode Coatings in summary

Feature INEOS vs Competitor

Over potential In trials in other technologies INEOS’ over potential at start-up is the same as non precious metal coatings but demonstrates better performance over a longer lifecycle.

Resistance to reverse currents at shutdown

INEOS cathode coatings lose no catalyst when subjected to reverse current..

Non precious metal coatings are known to be attacked by reverse currents

Resistance to impurity poisoning

High surface area minimises the sensitivity to impurity damage.

Any poisoning that does occur tends to be reversible (e.g. at shutdown)

Lifetime Experience indicates INEOS cathode coatings will last for >16 years

Proven in FM mono-polar electrolysers over 18 years,

13 years (and counting) without weight loss in BICHLOR™ bipolar electrolysers

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INEOS REFURBISHMENT CAPABILITY

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INEOS Refurbishment Facility

• A new purpose built facility commissioned in Q1 2013.

• First delivery within 4 weeks from initial receipt of pans.

• Smaller batches can be accommodated in a shorter lead time.

• In addition to modular type electrolysers, different types of structures may be processed for example mercury and large fly screen meshes.

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Refurbishment Process

� Receipt and identification

� Pre-work inspection & assessment (Recorded in database)

� Refurbishment - Repair (Mesh, Flange and Pan repair)

� Surface preparation

� Coating

� Final quality inspection

� Packing & Dispatch

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Inspection

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Expert Welding

Fine ‘jewellery’ type welding by experts

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Refurbishment – Flange and electrode damage/corrosion

crevice corrosionflange corrosion

Corrosion at compression points Corrosion of louver

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Louvre Replacement

Sections of corroded louvre are removed and replaced

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Inlet Repair

Corrosion to outlet pipe

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Inlet Repair

Completed Repair

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Key Steps – Surface Preparation

ANODE

CATHODE

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Pan/Element Washing

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In-Pan/Element Coating

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In-Pan/Element Coating

Flange protected by coating

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Final Inspection

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Finished Product – Preparing for Shipment

SUMMARY

INEOS CAN PROVIDE :-

� STATE OF THE ART COATINGS• Long life• Robust against wear, reverse currents and impurities• Low over voltage

� COMPREHENSIVE RE-COATING AND REFURBISHMENT SERVICE