BIMETALLIC CORROSION WORKSHOP PRESENTATION ON 01 – 02 JUN 2017

PRESENTATION 02: BARRIERS vs. SEALS PRESENTED BY: AFRISUN COATING ENTERPRISES (PTY) LTD PRESENTER: DANIEL VAN DER WESTHUIZEN PRESENTATION 02: BARRIERS vs. SEALS

PROTECTIVE COATINGS (TWO TYPES) PASSIVE BARRIER ACTIVE SEAL

PROTECTIVE COATINGS PASSIVE BARRIER EPOXIES POLYURETHANES INORGANIC ZINC COATINGS POLYSILOXANE (SILICONE) PASSIVE BARRIER INERT LAYER OF COATING FORMING A SHELL OVER THE SURFACE WEAKNESS : HARD & CRACK - ALL STRUCTURES MOVE NO CHEMICAL REACTION WITH METAL LEADS TO UNDERCREEPAGE

PASSIVE BARRIER FAILURE

PASSIVE BARRIER FAILURE

PASSIVE BARRIER FAILURE

REACTS WITH THE SURFACE OF THE SUBSTRATE PROTECTIVE COATINGS HOT DIP GALVANIZING HIGH RATIO CALCIUM SULFONATE ALKYD COATINGS (HRCSA) ACTIVE SEAL REACTS WITH THE SURFACE OF THE SUBSTRATE

HOT DIP GALVANIZING PROVIDES ACTIVE BARRIER PROTECTION Zinc Carbonate Layer (Not easily removed) * Will discuss this later CATHODIC PROTECTION – Zinc is electro negative to carbon steel Zinc is - sacrificial Anode Carbon Steel - protected Cathode CARBON STEEL IS ONLY PROTECTED WHILE ZINC IS PRESENT.

PREVENTS UNDERCREEPAGE – ACTIVE SEAL CATHODIC PROTECTION PREVENTS UNDERCREEPAGE – ACTIVE SEAL

HOW TO MITIGATE BIMETALLIC CORROSION? Eliminate the electrolyte or Prevent the flow of electrical current Prevent oxidation Modify the environment

WHAT ABOUT A COATING THAT CAN PROVIDE ALL OF THESE? Eliminate the corrosion cell (exclude electrolyte) & Prevent the flow of electrical current (bad conductor) Prevent oxidation (exclude oxygen) Modify the environment (raise the pH > 10) HIGH RATIO CALCIUM SULPHONATE ALKYD - (HRCSA)

HRCSA COATING: PERFORMANCE BY FORMULATION HIGH CORROSION RESISTANCE – Due to the chemical reaction of the mild sulphonic acids in the HRCSA with the Zinc Carbonate Layer (not easily removed) on the metal surface the pH > 10.1. This modified environment actively mitigates corrosion.

HRCSA COATING: PERFORMANCE BY FORMULATION HIGH RESISTANCE TO UNDER-CREEP - high affinity of the calcium sulphonate for bare metal resists the formation of under-creeping ADHESION BY MEANS OF VAN-DER-WAALS FORCES – POS & NEG ATTRACTION

HRCSA COATING: PERFORMANCE BY FORMULATION MOISTURE DISPLACEMENT - HRCSA has a higher affinity for metal than water (hydrophobic). The Calcite (CaCO3) platelets prevent oxygen and water from reaching the substrate, eliminating the electrolyte needed for corrosion and oxygen needed for oxidation

HRCSA RED PENETRANT & TOP COAT HRCSA IS HIGHLY COMPATIBLE WITH CONCRETE

ELECTRICAL CONDUCTIVITY - HRCSA is not a good conductor of electricity ELECTRICAL CONDUCTIVITY - HRCSA is not a good conductor of electricity. Stray electric currents accelerate corrosion. HRCSA is effective in metal joints and seams where stray currents would concentrate

HIGH RATIO CALCIUM SULPHONATE ALKYD (ANTICORROSION COATING) Formulated as an overcoat & encapsulating system for Red lead based coatings Hot dipped galvanizing Aluminium-Zinc coatings Zinc-rich primers & topcoats Direct to metal and concrete Passive barrier coatings (except silicone, bitumen)

CHEMISTRY OF THE HRCSA I’m now going to ask Rick Noles from Watson Coatings Inc. to explain the chemistry behind the coating, making it an Active Seal, stopping bimetallic corrosion. He will also give you and indication of the testing that was done as well as where the coating has been applied in the USA.

I THANK YOU. ARE THERE ANY QUESTIONS I THANK YOU! ARE THERE ANY QUESTIONS? AFRISUN COATING ENTERPRISES (PTY) LTD 012 662 0330 / 082 789 2582