PRESENTATION ON 01 02 JUN 2017 PRESENTED BY AFRISUN COATING ENTERPRISES PTY LTD PRESENTER DANIEL VAN DER WESTHUIZEN PRESENTATION 02 BARRIERS vs SEALS PROTECTIVE COATINGS ID: 681361
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Slide1
BIMETALLIC CORROSION WORKSHOP
PRESENTATION
ON 01 – 02 JUN 2017Slide2
.
PRESENTED BY
:
AFRISUN COATING ENTERPRISES (PTY) LTD
PRESENTER: DANIEL VAN DER WESTHUIZEN
PRESENTATION 02:
BARRIERS vs. SEALSSlide3
PROTECTIVE
COATINGS
(
TWO TYPES
)
PASSIVE BARRIER
ACTIVE SEALSlide4
P
ROTECTIVE COATINGS
PASSIVE BARRIER
EPOXIES
POLYURETHANES
INORGANIC ZINC COATINGS
POLYSILOXANE (SILICONE)
WEAKNESS :
HARD
&
CRACK
-
ALL
STRUCTURES MOVE
NO CHEMICAL REACTION WITH METAL LEADS TO UNDERCREEPAGE
INERT
LAYER OF COATING FORMING
A SHELL OVER THE SURFACESlide5
PASSIVE
BARRIER FAILURESlide6
PASSIVE BARRIER FAILURESlide7
PASSIVE BARRIER FAILURESlide8
PROTECTIVE COATINGS
ACTIVE
SEAL
HOT DIP GALVANIZING
HIGH RATIO CALCIUM SULFONATE ALKYD COATINGS (
HRCSA
)
REACTS WITH THE SURFACE OF THE SUBSTRATESlide9
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 CathodeCARBON STEEL IS ONLY PROTECTED WHILE ZINC IS PRESENT.Slide10
CATHODIC PROTECTION
PREVENTS UNDERCREEPAGE – ACTIVE SEALSlide11
HOW TO MITIGATE BIMETALLIC CORROSION?
Eliminate the electrolyte
or
Prevent the flow of electrical current
or
Prevent oxidation
or
Modify the environmentSlide12
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 (
r
aise the pH > 10)
HIGH RATIO CALCIUM SULPHONATE
ALKYD - (HRCSA)Slide13
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.Slide14
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 ATTRACTIONSlide15
HRCSA COATING: PERFORMANCE BY FORMULATION
MOISTURE
DISPLACEMENT
- HRCSA
has a higher affinity for metal than water (hydrophobic).
The
Calcite
(CaCO
3
)
platelets
prevent oxygen
and
water from reaching the substrate, eliminating the electrolyte needed for corrosion and oxygen needed for oxidationSlide16
HRCSA RED PENETRANT & TOP COAT
HRCSA
IS HIGHLY COMPATIBLE WITH CONCRETESlide17
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 concentrateSlide18
HIGH RATIO CALCIUM
SULPHONATE
ALKYD
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)(ANTICORROSION COATING)Slide19
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.Slide20
I THANK YOU!ARE THERE ANY QUESTIONS?
AFRISUN COATING ENTERPRISES (PTY) LTD
012 662 0330 / 082 789 2582