1. BIMETALLIC CORROSION WORKSHOP
PRESENTATION
ON 01 – 02 JUN 2017

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

3. PROTECTIVE COATINGS (TWO TYPES)
PASSIVE BARRIER
ACTIVE SEAL

4. 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

5. PASSIVE BARRIER FAILURE

6. PASSIVE BARRIER FAILURE

7. PASSIVE BARRIER FAILURE

8. 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

9. 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.

10. PREVENTS UNDERCREEPAGE – ACTIVE SEAL
CATHODIC PROTECTION
PREVENTS UNDERCREEPAGE – ACTIVE SEAL

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

12. 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)

13. 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 > This modified environment actively mitigates corrosion.

14. 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

15. 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

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

17. 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

18. 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)

19. 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.

20. I THANK YOU. ARE THERE ANY QUESTIONS
I THANK YOU! ARE THERE ANY QUESTIONS? AFRISUN COATING ENTERPRISES (PTY) LTD /