1. Condition Assessment and Environmental
Ranking of Weathered T&D Structures and
Equipment; Evaluation and Testing of Coatings
for
Electrical Transmission and Substation
Structures and Equipment

2. Topics For Today
• Overview and History of T&D Coatings.
• Focus on: Above-grade lattice Towers,
Transmission Poles, Substation Structures.
• Aged Galvanized Steel, Overcoating Aged Coatings,
Rusted Carbon Steel Structures.
• Evaluate Substrates and Environment.
• Evaluate Coatings Specified.

5. The Basic Idea
• Create a working maintenance painting program
for electric utilities to protect hundreds of
thousands of T&D assets utilizing a full survey of
the environmental corrosion potential, the
substrate conditions, and the priorities of the
owner; normally resulting in specifications for one-
coat systems, or minimal sealing/priming, after
minimal (SSPC-SP2) Surface Preparation (maximum
SSPC-SP3)..above-grade.

7. Common Coating Systems
• One-coat coating systems for weathered
galvanized steel. (SSPS-SP2)
• Spot prime with rust penetrating sealant and full
coat of one-coat tower paint. (SP2) and/or spot
SP3 cleaning.
• Full prime or penetrating sealant and one full coat
of tower paint. (SSPC-SP3 full or partial as
required)

9. Towers by Install Date USA
30000
25000
20000
15000
10000
5000
0
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

10. Cost Effective Approach
• Also for Communication towers, Railroad and
highway bridges, highway sign posts, guard rails,
chain-link fencing, quonset huts, some metal roofs,
pre-fab buildings, and distribution poles. The list is
limitless; and massive cost savings to the owners
and tax-payers, and much more sustainable than
replacement with new galvanized or painted
carbon steel.

13. Back to the Future
• Oldest surviving basic technology to still be sole-
sourced since 1955. Many high-performance
coatings developments are tied to significant
cleaning and surface preparation requirements,
which sometimes trigger extreme controls on
environmental costs (full-containment) and other
expensive requirements. Lowest cost per square
foot per year @ 20-30 years life.

17. Ancient History
• Resin System=Drying Oils= Pressed flax-seed oil=
Linseed Oil+ modification=Excellent wetter.
• In use for hundreds of years; first used as varnish..
Absorbs oxygen from the air and cures outside/in,
or top down. 30 days to through dry and 1 year to
harden enough for accelerated testing.
• Originally used with lead pigments as industrial
coating + barrier pigments.

18. Linseed Oil Wetting and Penetration

19. Basics of This Type of Approach
• Minimize Cleaning and Surface Preparation Costs.
• Minimize Removal of Sound Existing Coatings.
• Minimize Generation of Hazardous Waste.
• Minimize Costs associated with full containments,
air-fed respirators, etc.
• Maximize corrosion protection with minimal life-
cycle costs= Functional protection vs. aesthetics.

20. T&D Maintenance Program
• Assess Stage of Aging • Survey Structures Past
(New, Partially “Optimal Window of
Weathered, toast. Opportunity.”
• Predict “Time to First • Digitize data base,
Maintenance” of all pictures, and
T&D structures. spreadsheets.
• Create Pro-Active • Continuously Monitor
Corrosion Protection your Program.
Program.

21. Standards, Classifications, Rankings,
Visual Guides vs. 1980s (none)
• ISO 9223: This standard classifies the corrosivity of
an atmosphere based on measurements of time of
wetness, and pollution categories (sulfur dioxide,
airborne chlorides), UV, et.al..
• ISO 12944: Basic C-1 through C5i and C5m.
• NACE: Standards, Surface Prep Standards

23. More Standards Organizations
• NACE: Standards, Surface Prep Standards
• ASTM: Test Procedures, Standards (D610 -08),
adhesion D-3359, et. al..
• IEEE: Joint Standards with NACE for T&D!
• EPRI: Scientific Research & advanced equipment.
• SSPC: QP Programs, Surface Preparation
Standards (SSPS-VIS2 and SSPC-VIS3)

24. NACE/IEEE
• STG 41 - Electric Utility Generation, Transmission,
and Distribution
• TG 395 - Atmospheric (Above-Grade) Corrosion
Control of Transmission, Distribution, and
Substation Structures by Coating Systems
• TG 386 - Below-Grade Corrosion Control of
Transmission, Distribution, and Substation
Structures by Coating Systems

25. Life-Cycle of New Galvanized
• Removed from molten zinc bath: Phase N1
• Pure zinc layer reacts with oxygen(O2)> forms
zinc oxide (OH)2: First 48 hours. Phase N2
• Zinc oxide reacts with moisture, and forms
zinc hydroxide: Zn (OH)2. 48 hours to 6
months. Phase N3

27. Life-Cycle of New Galvanized
• Zinc hydroxide exposed to more O2 and
carbon dioxide (CO)2, and forms Zinc
Carbonate. 2ZnCO3> Zn(OH)2. Now has a
stable oxide (protective oxide or patina layer
for up to 2 years zinc surface is active). Phase
N4
• “Aged galvanized” > 2 years.

28. Categories of Aged Galvanized
• Up to 2 years: New (Special methods to clean and
prepare surface) = “New Galvanized”= Phase A1
• From 2 years to first signs of corrosion: Most of
original galvanized layer remains; minimal to no
zinc-iron alloy staining or rust is evident. Surface
may stay this way for over 20 years. = “Partially
Aged Galvanized,” or Phase A2.

29. Categories of Aged Galvanized
• Aged Galvanized (First signs of corrosion
pattern; such as edges. Galvanized layer
becomes thinner; up to 10% rusting.= “Aged
Galvanized,” Phase A3.

30. Condition Assessment
• 10-50% Rusting and less than 2 mils of zinc-iron alloy layer
remaining. Lots of staining and abrasive rusting. = Phase
A4
• Greater than 50% rusted. Minimal to zero zinc-iron alloy
layer remaining. Staining and rust cover > 90% of the
structure. = Phase A5
• Beyond Condition 5 the structure may need to be repaired
or replaced. Heavy pitted rusting over the entire
structure. Phase A6

32. C1 Rural areas, low pollution. Heated
C2
buildings/neutral atmosphere.
C3 Urban and industrial atmospheres.
Moderate sulphur dioxide levels.
Production areas with high humidity.
C4 Industrial and coastal.
Chemical processing plants.
C51 Industrial areas with high humidity and
aggressive atmospheres.
C5m Marine, offshore*, estuaries, coastal areas
with high salinity.

33. ISO 9223
Category Short Term Corrosion Rate Long Term Corrosion Rate
(g m-2 year-1) (mm year-1)
C1 CR <= 10 CR <= 0.1
C2 10 < CR <= 200 0.1 < CR <= 0.5
C3 200 < CR <= 400 1.5 < CR <= 6
C4 400 < CR <= 650 6 < CR <= 20
C5 650 < CR 20 < CR

34. TOW: Time of Wetness
• TOW units are hours per year (hours/year) when relative
humidity (RH) > 80% and the temperature > 0oC.
• TOW <= 10 T1
• 10 < TOW <= 250 T2
• 250 < TOW <= 2,500 T3
• 2,500 < TOW <= 5,500 T4
• 5,500 < TOW T5

36. Sulphur Dioxide (SO2) Levels
• SD <= 10 P0
• 11 < SD <= 35 P1
• 36 < SD <= 80 P2
• 81 < SD <= 200 P3
• The units used for the sulfur dioxide categories in
the ISO 9223 are as sulfate deposition (SD) rate in
mg m-2 day-1.

38. Airborne Chlorides
• The units used for the chloride categories
(airborne salinity) in the ISO 9223 are as chloride
deposition (CD) rate in mg m-2 day-1:
• CD <= 3 S0
• 4 < CD <= 60 S1
• 61 < CD <= 300 S2
• 301 < CD <= 1,500 S3

39. Atmospheric Contaminants
• Atmospheric contaminants such as hydrogen
sulfide, hydrogen chloride and chlorine
present in the atmosphere can intensify
atmospheric corrosion damage, but they
represent special cases of atmospheric
corrosion, normally related to industrial
emissions in specific micro-climates.

40. Combine the Rankings
• For example; if you have a lattice-tower in a C3
environment, and it is a Condition Ranking of A3, a
Specification for surface preparation and coating
would be generated by that combination:
• SSPC-SP2 Hand Tool Cleaning
• Primer/Finish: One coat of modified linseed oil
MIO/Zinc dust tower paint applied at 8-10 mils=
20-25 years of corrosion protection.

41. UV Precipitation Acid Rain Airborne Air Chlorides
INDEX TOW INDEX Corrosives Pollution
Specific Index
Source
Coastal Low Medium-High Medium P&P Mill Low- High
Maine Medium
Vegas Very Very Low Very Low
High
Los
Angeles
North Very
Pole Low
China
Caribbe
an
Texas High Low Low High High High

42. More Severe Combinations
• S3 Ranking for Airborne Chlorides= Severe.
• P3 Ranking for So2=Severe.
• T5 Ranking for Time of Wetness= Severe.
• UV5 Ranking For Ultra Violet Rays= Severe.
• X5 Ranking for Other Atmospheric Contaminants=
Severe.
• Severe rankings in all categories are rare.

43. Micro-environments= Isolated
Environmental Contaminants
• Specific to small numbers of towers on a long line.
• Chemical Plants
• Pulp & Paper Mills
• High-Humidity Low Rain Areas
• May require more chemical resistant coatings;
minor % of the total.

48. Essential Properties of Coating
• Maximum wetting and penetration into tight
corroded spaces.
• High-build; 9- 11 mils WFT in one coat= 8-10 mils
DFT.
• Easy to apply by mitt or pound brush.
• Maximum barrier properties to resist moisture,
airborne chlorides, chemicals, air pollutants, and
ultra-violet light.

49. Candidate Coatings For Structures
• Modified Linseed-Oil Zinc-Dust.
• Modified Linseed-Oil MIO/Zinc-Dust.
• Modified Linseed-Oil MIO/Zinc-Dust, Aluminum,
and Ceramic Microspheres.
• Aluminum Epoxy Mastics.
• Calcium Sulfonate Alkyds.
• Epoxy Penetrating Sealers.

50. Benefits of Penetrating Sealers
• Tie-down existing old coatings; wick under
loose edges and into tight crevices.
• Very low viscosity.
• No curing stresses that pull off old coatings.
• 100% SBV
• Tougher and more moisture and chemical
resistant than alkyd primers.

51. MIO as Barrier Pigment
• Chemically Inert and very resistant to pollution.
• Does not react with high or low pH. (acid and
alkaline resistant)
• Labyrinth Effect and Shielding from UV, pollution,
and especially moisture.
• Absorbs UV and warms the coating; hence drying.
• Promotes adhesion to substrate and itself.

53. MIO: 100 Years of Success
• Is Non-Toxic, Non-Oxidizing, Non-Corrosive &
Non-Flammable. With such excellent chemical
& environmental properties, it is not a
surprise that it is the world’s most favored
barrier pigment for over 100 years.
Formulators consider MIO to be a key weapon
in their anti-corrosive arsenal.

54. MIO as Barrier Pigment
• Improved mechanical properties.
• Less cracking
• Tougher coating all around.

55. Properties of Ceramic Microspheres
• Reduces Undercutting and improves
resistance to cathodic disbonding
• Enhances Film-Build and especially edge
retention on towers.
• Lowers Permeability of the paint film.

56. Composition
Minimal Solvent
Ceramic Beads Minimal VOC’s
Hydrophobic Carbon Modified Linseed Oil Alkyd Binder No Haps
SUBSTRATE

57. Contractor Qualifications
•Adult CPR, AED, and Community First Aid
•High Voltage Electrical Safety for Power Generation, Transmission, &
Distribution (required OSHA rule 1910.269)
•Fall Protection
•Tower / Pole Rescue
•OSHA 10-hour Safety Training
•Lead Awareness and Hazard Communication
•*OSHA 30-hour Supervisor Safety Training
•Lead Removal and Safe Operating Procedures
•Hazardous Waste Operations and Emergency Response
•* Lift / Boom Operations and Safety
•* CCS-lhf1 and Permit Required Confined Space certification
•* SSPC C-3 Supervisor / Competent Person
•* NACE Certified Coating Inspector

58. Tower Footings
• 1930s and 1940s: Dipped in hot tar. No longer
specified. Under-film corrosion. Coal-tar epoxy
used in 1960s-1980s. Not often specified; also
strong cohesion vs. sub-film corrosion. Results
improved when 110 micron HDG was increased to
200 microns. More awareness of conductivity (soil
resistivity) pH values, types of soils, et. al.. 0.5 mm
zinc plates welded to tower legs on all sides.

60. Tower Footing History
• Zinc plates welded plus hot tar dips.
• Tapes used 1955-1980s: Freeze-thaw issues.
• Copper earth mats: tower leg becomes the anode=
500 microns per year of corrosion.
• Moisture-cured coal-tar urethanes frequently used
today (limitations on surface preparation costs and
time)

61. Complex Configurations

64. VOLTAGE MINIMUM
DISTANCE
50 - 1,000 Avoid Contact
1,100 - 15,000 2’ 2”
15,100 - 36,000 2’ 7”
36,100 - 46,000 2’ 10”
46,100 - 72,500 3’ 6”
72,600 - 121,000 4’ 3”
138,000 - 145,000 4’ 11”
161,000 - 169,000 5’ 8”
230,000 - 242,000 7’ 6”
345,000 - 362,000 12’ 6”
500,000 - 550,000 18’ 1”