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

2. PRESENTATION 03: ESKOM EVALUATION.
PRESENTED BY:
AFRISUN COATING ENTERPRISES (PTY) LTD
PRESENTER: DANIEL VAN DER WESTHUIZEN
PRESENTATION 03: ESKOM EVALUATION

3. DUPLEX- & OVERCOAT SYSTEM
Uncontrolled steel chemistry
Serious problem for Eskom steel lattice electrical towers
Looking for a duplex coating over galvanized steel to mitigate corrosion

4. PROBLEM : STEEL CHEMISTRY
HDGASA
We are confronted with imported steel chemistry that is not always conducive to a quality hot dip galvanized finished
product
Imported steel have shown that the percentage Si and P content is not controlled, leading to differences in hot dip galvanized steel surface finishing’s
Uncontrolled steel chemistry has a direct influence on the quality of the surface finish of hot dip galvanized steel
Volume 10 Issue Hot Dip Galvanizing Today

5. GALVANIZING PROCESS
During galvanizing the article is completely immersed in a bath of molten zinc between 435º - 455º C.
The chemistry of the bath is at least 98% pure zinc in accordance with ASTM B6.
The zinc reacts with the iron in the steel to form a series of metallurgical bonded zinc-iron alloy layers.

6. STEEL CHEMISTRY Silicon < 0.03% and zinc temperature 450°C
- Zinc coating thicknesses range between 50 µ to 65 µ
Silicon > 0.15% to < 0.25% and zinc temperature 450°C
– Zinc coating thicknesses range between 120 µ to 200 µ
Phosphorous < 0.01% preferred
> 0.02% Zinc coating excessively thick > 200 µ
- Brittle, susceptible to chipping or flaking

8. THE SANDELIN CURVE
The Sandelin curve, compares the zinc coating thickness to the mass percentage of silicon in the steel.
The area on the graph labelled “I” is called the Sandelin area. The coatings in “I” tend to be thick and dull grey.
This area is known as the Sandelin range since Dr. Sandelin, a metallurgist, performed the experimental work to show this behaviour of galvanized steel.
The Sandelin area is roughly between 0.05% and 0.15% silicon.
The area on the graph labelled “II”, which represents a steel content of greater than 0.25% silicon, shows the coating thickness increases with increased silicon content and then starts to level off at around 0.4% silicon.

9. Alloy Layers in Galvanizing
DPN - Diamond Pyramid Hardness Number

10. Relationship between dipping time and thickness of zinc coating in steels with different silicon contents.

11. ENVIRONMENTAL CONDITIONS
Depletion rate of Zn depends on the period of time and environmental conditions the galvanized structure has been exposed to.
Lifecycle of the galvanizing depends on the applied or specified DFT.

12. KIPTS EVALUATION: DUPLEX- & OVERCOAT SYSTEM
Eskom LES requested that the HIGH RATIO CALCIUM SULPHONATE ALKD (HRCSA) branded as ARMOR-SHIELD CSA be tested before any application to steel will be considered.

13. EVALUATION
HIGH RATIO CALCIUM SULFONATE ALKYD (HRCSA) AS AN ACTIVE DUPLEX COATING FOR GALVANIZED STEEL

14. ESKOM EVALUATION Nov 2013 – Nov 2015
LOCATION: Koeberg Insulator Pollution Testing Station (KIPTS)
POLUTION LEVEL: CX5+ (ESKOM)
DURATION: 24 MTHS

15. KIPTS EVALUATION: DUPLEX- & OVERCOAT SYSTEM
TO DETERMINE PRODUCT PERFORMANCE BASED ON VARIOUS DEGREES OF SURFACE PREPARATION PROCEDURES DUE TO ON-SITE APPLICATION
KIPTS 2nd HIGHEST POLLUTION ZONE IN THE WORLD

16. KIPTS EVALUATION: PREPARATION PROCEDURES No Prep
Wire brushing & dusting
Wire brushing & water washing
Wire brushing, water washing with salt removal additive

17. SAMPLES PROVIDED OLD & NEW GALVANIZED STEEL

18. SAMPLES MOUNTED Then coated with ARMOR-SHIELD CSA

19. NEW GALVANIZING
SURFACE PREP: NONE
8760 HRS
13 Nov 2014
13 Nov 2013

20. NO CORROSION OR
UNDERCREEPAGE

21. NO UNDERCREEP OR CORROSION AT SCRIBE
27 Months
815 Days
Hours
NO UNDERCREEP OR CORROSION AT SCRIBE

22. CX 5+ ENVIRONMENT 8760 HRS 13 Nov 2013 13 Nov 2014
PANEL: Grit Blasted (near white metal) Single coat Armor-Shield CSA
CX 5+ ENVIRONMENT
8760 HRS
13 Nov 2013
13 Nov 2014

23. 31 MTHS – 21 400 HRS PANEL GRIT BLASTED TO NEAR WHITE METAL
FULLY COATED WITH ARMOR-SHIELD CSA
31 MTHS – HRS

24. CLOSE-UP OF SCRIBE
AFTER 31 MTHS – HRS
NO CORROSION OR UNDERCREEPAGE AT SCRIBE - CSA IS AN ACTIVE BARRIER

25. BACK OF PANEL
AFTER 31 MTHS – HRS
NO PROTECTION

26. NOV 2013 PANEL (OVERCOATED) GRIT BLASTED TO NEAR WHITE METAL
FULLY COATED WITH EPOXY
THEN ½ COATED WITH ARMOR-SHIELD CSA
EACH HALF SCORED
NOV 2013

27. NOV 2014 (12 months later) CORROSION & UNDERCREEPAGE ON EPOXY
(PASSIVE BARRIER)
NO CORROSION OR UNDERCREEPAGE ON CSA
(ACTIVE BARRIER)

28. ENLARGED PIC NO PROTECTION AT SCRIBE DIRECT CONTACT WITH ATMOSPHERE
UNDERCREEPAGE
CAUSING DELAMINATION
AND ACCELERATED CORROSION

29. ARMOR-SHIELD CSA TOPCOAT AS AN OVERCOAT
PROVIDES PROTECTION AGAINST CORROSION

30. An Investigation Into The Methodology To Develop An Insulator Pollution Severity Application Map For South Africa by D Pietersen, JP Holtzhausen, and W.L. Vosloo
“Corrosivity and insulator pollution levels at the coast (KIPTS) are 2-3 times those at sites 800 m from the coast, reflecting the exceptional pollution concentration over the first few hundred meters from the seacoast, which is
mainly attributed to the high NaCl (salt) concentration levels and high relative humidity in the region closer to the coast.”

31. ARMOR-SHIELD CSA : CONCLUSION OF TEST
Taking into consideration the severe environmental conditions found at Koeberg Insulator Pollution Testing Station (KIPTS) which is classified as a CX5+ pollution environment and being exposed to natural weathering for hours (24 months), the local South African hours Salt Test (ASTM B117) result and the extensive Accelerated Laboratory Tests (ALT) done for the FEDERAL HIGHWAY ADMINISTRATION by the Turner-Fairbanks Research Centre for hours, the performance of the HRCSA clearly indicates that this coating, based on Calcium Sulphonate Alkyd (CSA), is the ideal duplex coating over galvanizing and the best coating to protect steel against corrosion.

32. 3RD PARTY TESTING IN USA U.S Army Corps of Engineers (2 866 hrs)
PowerTech Inc. – Canada
(4 000 hrs)
Kentucky Transport Authority
(5 000 hrs)
Federal Highway Authority
(ALT – hrs)
(Marine – 24 month) – Outdoor
Nov 2012
DEC 2003

33. FHA TEST RESULTS: SALT SPRAY (6 840 HRS)
EPOXYMASTIC
CALCIUM SULPHONATE ALKYD

34. ARMOR - SHIELD CSA
Passes the Toughest of Industry Testing for Long Term Performance
RATING
ASTM D4838 Colour
ASTM D7114 Blistering
ASTM D1654 Rust Undercutting
ASTM D 5767 Gloss
ASTM D Cyclic Salt Fog /
UV Exposure of Painted Metal
ASTM D522 Mandrel Bend Test (3.2 mm) - 180º (Passed)

35. SA SALT FOG TEST RESULTS (ASTM B117) 1 500 HRS
The coating showed no defects after 1500h salt fog exposure.
A cross cut scribe was made through the coating down to the metal substrate and no under-film creep occurred at this scribe mark during the test period.
Testing Laboratory:
Metlab Germiston
(SANAS approved)

36. SA SALT FOG TEST RESULTS (ASTM B117) 1 500 HRS
Discussion of Results
The results showed excellent corrosion protection for the period tested [1500h].
Rule of thumb h salt spray exposure test = 3 yrs marine exposure

37. ARMOR - SHIELD CSA ADVANTAGES NO DAMAGE TO GALVANIZING
NO ENVIRONMENTAL CONTAMINATION
NO HEALTH & SAFETY CONCERNS (CURED COATING IS NON-TOXIC)
QUALITY CONCERNS – DO NOT NEED TO DISMANTLE STRUCTURES
VERY COST EFFECTIVE PROCESS (LONG LIFE CYCLE)

38. CORROSION PREVENTION COAT IT WITH ARMOR-SHIELD CSA!
THE ONLY ACTIVE PROTECTION SYSTEM OF IT’S KIND!

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