CHLORIDES the CORROSION CHALLENGE Charles F. Lawrence, P.E. NACE International Cathodic Protection Specialist

Why Does Corrosion Occur?

The Corrosion Cell Me Me Corrosion Battery ANODE CATHODE ELECTROLYTE + ne - Corrosion Battery Closure Circuit e - CLOSURE CIRCUIT Anode ANODE Cathode CATHODE Electrolyte (water) Me + OH - H ELECTROLYTE

Real World Corrosion + e-

Fe+ 3 + O= = Fe2O3 Fe+ 3 + Cl- = FeCl3 The Chloride Difference Insoluble Fe+ 3 + O= = Fe2O3 Fe+ 3 + Cl- = FeCl3 Very Soluble

Corrodible Things Infrastructure Equipment Pipelines Roads Bridges Automobiles Trucks/ Plows Loaders

Infrastructure Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl-

Possible? Solutions No salt Less salt Construction practices Coated rebar Fiberglass rebar Denser concrete / cover Overlays Maintain coating Metalizing

Equipment

Possible? Solutions Remove salt residue frequently Non-metallic components Metalized components Better coatings Maintain coatings Scrupulously maintain lubrication Add corrosion inhibitors

Damaging to vegetation Salt Sodium Chloride (NaCl) PROS CHEAP Readily available Works to 20°F Stable in storage Easily applied CONS Corrodes metals Only works to 20°F Damaging to vegetation Pollutes waterways Contaminates soils

Salt (NaCl) Alternatives 1. Sand / Cinders PROS Works to 0°F Safer for animals and vegetables Doesn’t leave a powdery residue CONS More expensive (2X) Still corrosive (14% more Cl-) Very hygroscopic, keeps surfaces wet Forms greyish gooey coating PROS Works to -25°F Exothermic More hygroscopic Less harmful to vegetation CONS More expensive (3X) Still corrosive (3% more Cl-) Leaves a white residue PROS Can be used with or instead of brine Lowers melt temp by 10°F Sugars are less corrosive Relatively inexpensive Helps stick to pavement CONS Bloody mess Sticks to vehicles Nutrient load on streams PROS Works to -2°F Environment and animal friendly Timed release Prevents ice from sticking to surfaces Safe for pavement CONS More expensive (8X) Not readily available in bulk PROS May be free Somewhat better than regular brine CONS Similar corrosion issues to regular brine PROS Essentially non-corrosive Provides good traction Temperature independent CONS Does not eliminate ice Impact damage to vehicles / windshields Plugs storm sewers Silts waterways PROS Works to 21°F Acts as fertilizer Safer than salt for animals CONS Yuck factor More expensive (5X) Ineffective when very cold Most corrosive to concrete and masonry PROS Cheap Lowers the temperature limits of brine CONS Similar corrosion issues to Beet Juice PROS Works to -25°F Environmentally friendly? Less chlorides /# (10%) CONS May be expensive Slower melter PROS Works to -75°F Non-corrosive Biodegradable Less harmful to vegetation CONS More expensive (8X) Can cause slickness Low oxygen PROS Essentially non-corrosive Won’t harm vegetation Biodegradable CONS More expensive (20X) Only works to 25°F Subject to refreezing In large amounts can reduce waterways O2 levels PROS Works to 0°F Exothermic Quickly biodegradable Minimal toxicity CONS More expensive than Urea 2. Calcium Chloride (CaCl2) 3. Magnesium Chloride (MgCl2) 4. Potassium Chloride (KCl) 5. Beet Juice 6. Cheese Brine 7. Potato Juice 8. Urea 9. CMA – Calcium Magnesium Acetate 10. Potassium Acetate 11. Sodium Acetate 12. Safe Paw (amide / glycol)

Coatings Ideas Water-based acrylic polyurethane enamel paint Elastomeric Polyurethane Polyurea Polyaspartic Blends

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