Electric Utility Industry

Transmission Towers, Poles, Substation Structures and Equipment

Writing T&D coatings specifications using regional and global standards

NACE/IEEE “Atmospheric (Above-Grade Corrosion Control of Existing Electric Transmission, Distribution, and Substation Structures by Coating Systems” supplemented by ISO and ASTM Standards, global climate/weather and wind data, to predict corrosion rates, and to write T&D coatings specifications.

Incorporate environmental data and expanded condition assessment data into a software program that will select the appropriate cleaning, surface preparation, and coating system for any T&D coatings job.

Predictive Life Maintenance Program for Galvanized T&D Structures

Predict Life of New Galvanized Structures: Life prediction may vary by many decades, depending on multiple variables. Calculate the corrosion rate.

Schedule future maintenance according to anticipated life of galvanized structures.

Prioritize maintenance work based on minimizing cost and maximizing expected life of coatings.

Once optimal windows have been missed, priorities and costs will change.

Reactive maintenance programs more likely to sacrifice quality for cost= wait for galvanized to start failing.

Measure and Classify Corrosion Influences

More Corrosive Less Corrosive

Wet

Hot

Humid

Polluted Water

Polluted Air

Acids

Chlorides

Dry

Cold

Arid: Low Humidity

Clean Air

Clean Water

Neutral pH

Salt-Free

Charts all clearly show huge importance of environment on life of structure

Variable Life of Galvanized 85 years

Documented by ZALAS (Zinc and Lead Asian Service) are records of studies which conclude that in an (1)Arid Rural location zinc coating may last more than 100 years. In a (2) Rural location galvanized coating will last more than 90 years. In a (3) Mild Coastal environment where the air contains moisture with a salt (chloride) the zinc coating may last less than 50 years. In more hostile environment like a (4) Industrial location the life span of a galvanized coating reduces to more than 40 years compared to articles in a (5) Marine environment where coating life may be less than 20 years. Finally in a (6) Severe Marine location the anticipated life span of a galvanized coating is Less than 15 years. (Refer to Anticipated life of Zinc Coating Chart below): Some areas in South America have HDG failures in 5 years.

ISO 12944: Environmental

C1:Atmospheres with low level of pollution. Mostly rural areas.

C2:Urban and industrial atmospheres; moderate sulfur dioxide pollution.

C3:Coastal areas with low salinity.C4Industrial areas and coastal areas with moderate salinity.

C4-Industrial areas with high humidity and aggressive atmospheres. Also coastal and offshore areas with high salinity.

C5i and C5m- Include coastal marine and industrial marine; high humidity and aggressive atmospheres.

Similar to NACE IEEE Categories

Rural + definition=D= ISO C2, C3

Industrial/Rural + definition=C= ISO C3, C4

Marine + definition=B= ISO C4/C5m

Marine/Chemical + definition=A= ISO C5i and C5m

Category Steel Copper Aluminum Zinc

C1 CR <= 10 CR <= 0.9 negligible CR <= 0.7

C210 < CR <=

2000.9 < CR <= 5 CR <= 0.6 0.7 < CR <= 5

C3200 < CR <=

4005 < CR <= 12 0.6 < CR <= 2 5 < CR <= 15

C4400 < CR <=

65012 < CR <= 25 2 < CR <= 5 15 < CR <= 30

C5 650 < CR 25 < CR 5 < CR 30 < CR

Corrosivity Rates in Grams per square meter per year

ISO 12944 consists of the following parts, under the general title Paintsand varnishes — Corrosion protection of steel structures by protectivepaint systems:— Part 1: General introduction— Part 2: Classification of environments— Part 3: Design considerations— Part 4: Types of surface and surface preparation— Part 5: Protective paint systems— Part 6: Laboratory performance test methods— Part 7: Execution and supervision of paint work— Part 8: Development of specifications for new work and maintenanceAnnex A of this part of ISO 12944 is for information only.

ISO 12944 + NACE/IEEE StandardsProtective Paint Systems: Part 5: Tool to more accurate coating solutions. Coating system can meet both durability expectations and corrosion(environmental) category.

These tools can fine tune specifications; telling you when you might want to clean off contamination or not, add Power Tool cleaning to pitted areas or not, and add DFT mils to a coating system or not. It may also alert you that a different primer may be more applicable than another; for example a rust penetrating epoxy sealer instead of a more conventional primer; or a higher percentage of spot sealing/priming, et. al..

LocationType

AverageTemperature

RHIndex

UVIndex

PrecipitationIndex

Acid Rain Index

ChlorideIndex

AQIIndex

Rankings 1-5 1-5 1-5 1-5 1-5 1-5 1-5Arizona 4-5 1-2 4-5 1-2 1-2 1-2 2-3

UrbanNECoastal

2-3 3-4 1-2 3-4 3-5 4-5 2-3

HoustonMarine +Industrial

3-4 4-5 4-5 4-5 2-3 4-5 3-5

Industrial Non-Marine

1-5 1-4 3 2-5 3-4 1-3 4-5

Environmental Rankings by Location

Method and ModificationsEnvironmental Survey: Generate report with rankings.

Corrosion variables/intensifiers measured and ranked: Temperature, RH, precipitation/TOW, air quality (SO2, NOx), acid rain/ pH, ultraviolet exposure, et. al..

Assess condition of structures NACE IEEE R-1 through R-5, or (ISO 4628): Generate report with rankings+ corrosion rate.

Schedule time of first maintenance at the beginning of the life cycle of a structure.

Select a category for specified service life of coating system.

Write a coatings specification or long-term maintenance plan, with most variables taken into consideration.

ISO 9223, 9224, and 9225ISO 9223 “Corrosion of metals and alloys-Corrosivityof atmospheres-Classification” (Geneva, Switzerland: ISO, 1992)

ISO 9224 “Corrosion of metals and alloys-Guidingvalues for the corrosivity categories of atmospheres” (Geneva, Switzerland: ISO, 1992)

ISO 9225 “Corrosion of metals and alloys-Corrosivityof atmosphers-Measurement of pollution (Geneva, Switzerland: ISO, 1992)

ISO 9223:2012 classifies the corrosivity of an atmosphere based on various measurements.

This standard classifies the corrosivity of an atmosphere based on measurements of time of wetness, and pollution categories (sulfur dioxide, airborne chlorides). The standard was not intended to be used in extreme service

atmospheres such as those within chemical or metallurgical processing facilities or where there is direct contact with salt spray.

Sulfur dioxide may be expressed either in terms of a deposition rate or an airborne concentration. Either measure is to be made in accordance with ISO 9225. The units used for the sulfur dioxide categories in the ISO 9223 are as sulfate deposition (SD) rate in mg m-2 day-1.

SD <= 10 P0

11 < SD <= 35 P1

36 < SD <= 80 P2

81 < SD <= 200 P3

Measuring MicroenvironmentsThe corrosivity due to atmospheric conditions can be greatly affected by local conditions such as wind speed and direction, dust, debris, humidity, condensation and electrolytic species. These local conditions can change greatly within a few meters, depending on patterns in air turbulence. One extreme example of local variations due to the corrosivity of a seawater environment is the top deck of an aircraft carrier, where waves and seawater mist are abundant.

TOW (Time of Wetness)

TOW <= 10= T1

10 < TOW <= 250= T2

250 < TOW <= 2,500= T3

2,500 < TOW <= 5,500= T4

5,500 < TOW= T5

TOW units are hours per year (hours/year) when relative humidity (RH) > 80% and the temperature > 0oC.

Acidity in the Atmosphere

Acidity is described in terms of pH (the negative logarithm of the hydrogen ion concentration in a solution). pH scale ranges from 0 to 14 with 7, the midpoint, being neutral. Values less than 7 indicate progressively greater acidity, while above 7 are progressively more alkaline. Normal, unpolluted rain generally has a pH of about 5.6 due to carbonic acid created by CO2 in the air.

Acid Rain pH Map

Sources of Acid PrecipitationWhen atmospheric pollutants such as sulfur dioxide and nitrogen oxides mix with water vapor in the air, they are converted to sulfuric and nitric acids. These acids make the rain acidic, hence the term "acid rain". Rain returns the sulfur and nitrogen acids to Earth, and in high concentrations, can cause damage to natural environments including forests and freshwater lakes. This form of acid deposition is known as wet deposition.

Nitrogen compounds

Nitrogen compounds

Nitrogen oxides: highly reactive gases formed when nitrogen in fuel or combustion air is heated to temperatures above 650deg.C in the presence of oxygen, or when bacteria in soil or water oxidize nitrogen-containing compounds.

Nitrogen oxides combine with water to make nitric acid, which is a major component of atmospheric acidification.

Excess nitrogen also causes fertilization and eutrophication of inland waters and coastal seas.

Air Pollution Increases Corrosion

salt and water from ocean spray or road salt/water spray

just water + oxygen from the air (dampness accelerates corrosion rate)

fertilizers (as a dust) which contain salts other than NaCl

acids and alkalis (dust or spray)

hydrogen sulfide or sulfur dioxide

Table 18.2 -- Urban air toxics of greatest concern

Acetaldehyde Coke oven emissions Manganese compounds

Acrolein Dioxins Mercury compounds

Acrylonitrile 1,2-dibromoethane Methylene chloride

Arsenic compounds 1,3-dichloropropane Nickel compounds

Benzene Propylene dichloride Polychlorinated biphenyls

Beryllium compounds Ethylene dichloride Polycyclic organic matter

1,3-butadiene Ethylene oxide Quinoline

Cadmium compounds Formaldehyde 1,1,2,2-tetrachlorethane

Carbon tetrachloride Hexachlorobenzene Tetrachloroethylene (perchloroethylene)

Chloroform Hydrazine Trichloroethylene

Chromium compounds Lead compounds Vinyl chloride

Chemicals in the Atmosphere

Acid rain caused by SOx and NOx in the air can (and does) cause corrosion of metals and stone, as well as concrete.

Hydrogen sulfide can cause corroding of metals like iron and tarnish silver.

Salt spray can corrode iron and steel and erode concrete

Any material which is a powder or fume can deposit on surfaces and cause water and dew to wet the surface for a longer peiod of time - wet metals interact with oxygen and corrode faster.

How Airborne Pollution Increases Corrosion

Mapping Global Wind Patterns

ISO 4628 Evaluation of degradation of coatings

ISO 4628 is divided into 9 parts, each referring to different defects which can occur in paint coatings:

ISO 4628-1:2005 Part 1: General introduction and defect designation system

ISO 4628-2:2005 Part 2: Assessment of degree of blistering

ISO 4628-3:2005 Part 3: Assessment of degree of rusting

ISO 4628-4:2005 Part 4: Assessment of degree of cracking

ISO 4628-5:2005 Part 5: Assessment of degree of flaking

ISO 4628-6:2007 Part 6: Assessment of degree of chalking by tape method

ISO 4628-7:2005 Part 7: Assessment of degree of chalking by velvet method

ISO 4628-8:2007 Part 8: Assessment of degree of delamination and corrosion around a scribe

ISO 4628-10:2005 Part 10: Assessment of degree of filiform corrosion

All parts of the original standard have been transcribed for the Portuguese Standard, with the exception of

part 6 which is included in ISO 4628-6:2007.

Part 1 of the standard establishes a general system for designating the quantity, intensity and size of the

Life Cycle of HDGBrand New HDG – Five layers with a surface layer of 100% zinc. Spangled and shiny zinc metal color.Second Stage HDG – Pure zinc layer reacts with atmospheric oxygen (O2) and forms a zinc oxide (OH2) layer. This second stage is also unstable, as is the first stage, and will normally occur in the first 48 hours.Third Stage HDG – The zinc oxide layer reacts with moisture in the atmosphere and forms zinc hydroxide, which is also an unstable form of HDG requiring special procedures to properly coat. This third stage of HDG can take from 48 hours to six months to occur.

Eta, Zeta, Delta, Gamma, Steel

Stages of Weathered HDGFourth Stage HDG – Zinc hydroxide reacts with carbon dioxide in the atmosphere to form zinc carbamate, which is the first stage of “weathered galvanized” in that it is a stable form of zinc for coatings purposes. This stage can take from six months to two years to occur.Fifth Stage HDG (2nd stage of aged galvanized) – This A1 stage can take a short time to many decades to occur. It can be described as fully weathered galvanized HDG steel that has not yet begun to corrode, or has very little zinc/iron alloy layer showing with little to no staining from exposed layers of zinc/iron alloy exposure.Sixth Stage HDG (3rd stage of weathering) – <10% of the surface area showing signs of corrosion and/or zinc/iron alloy staining.Seventh Stage HDG (4th stage of weathering) – 10-50% of the surface area showing signs of corrosion and/or zinc/iron alloy staining.Eighth Stage HDG (5th stage of weathering) – 50-90% of the surface area showing signs of corrosion and/or zinc/iron alloy staining, and some pitting corrosion as well.Ninth Stage HDG (6th stage of weathering) – 100% of the surface area corroded, and little to zero galvanized remaining. Condition is closer to pitted corroded carbon steel, as no galvanized remains.

HDG Phases1. Initial oxidation 2Zn + O2 = 2ZnO (unstable)

2. Hydration 2Zn + 2H2O + O2 = 2Zn(OH)2 (unstable)

3. Carbonation 5Zn(OH)2 + 2CO2 = 2ZnCO3.3Zn(OH)2 + 2H2O (stable)

4. In salty air 6Zn + 4CO2 = 8NaCl + 7O2 + 6H2O = 4Zn(OCl)2 + 2Zn(HCO3)2 + 8NaOH (unstable)

5. Industrial atmospheres Zn + O2 + SO2 = ZnSO4

(unstable)

Categories for Water and Soil

Category Environment : Examples of Environment and Structures (IM3)

IM 1 Fresh water River installations, hydro-electric power plants.

IM 2 Sea or brackish water ..Harbor areas with structures like sluice gates, locks, jetties. Offshore structures.

IM 3 Soil. Tower footings, Buried tanks, steel piles, pipes.

Galvanic Scale

More Active To more nobleMagnesiumZinc (hot-dip, die cast, or plated) Cadmium (plated) Al 218 (die cast) Al 5052-H16 Tin (plated) Stainless steel 430 (active) LeadSteel 1010Iron (cast)Stainless steel 410 (active) Copper (plated, cast, or wrought) Nickel (plated)

Chromium (Plated) Stainless steel 310 (active) Stainless steel 301 (active) Tungsten Muntz Metal 280 Brass (plated) Nickel-silver (18% Ni) Stainless steel 316L (active) Bronze 220 Copper 110 Stainless steel 347 (active) Copper-nickel 715 Admiralty brass

New Galvanized Steel

Specifications A123/A123M or A153/A153M.

Chromate Quench or not. If not painting in 48 hours, and given sufficient moisture in air…

Wet storage stain vs. chromate layer removal.

New= Less than 48 hours old.

Partially Weathered= At least 48 hours to less than 2 years old.

Fully weathered= More than 2 years.

Each phase produces different variables.

Dissimilar metals

Stainless steel and aluminium are commonly used in contact with galvanizing, notably as fasteners and, except in very corrosive locations, are most satisfactory. However, copper and its alloys can accelerate the corrosion of galvanizing in corrosive situations, when in direct electrical contact. Corrosion products of copper and its alloys can also accelerate the corrosion of galvanizing.

RustFe2O3.H2O (hydrous ferrous oxide, sometimes written as Fe(OH)3) is the principal component of red-brown rust. It can form a mineral called hematite.

20.5 million tons of nitrogen oxides.

23.1 million tons of sulfur dioxide.

Definition of CorrosionPhysicochemical interaction between a metal and its environment which results in changes in the properties of the metal and which may often lead to impairment of the function of the metal, the environment, or the technical system of which these form a part. ISO 8044-1986

Corrosion is an irreversible interfacial reaction of a material (metal, ceramic, polymer) with its environment which results in consumption of the material or in dissolution into the material of a component of the environment. IUPAC

Preparing Hot-Dip Galvanized for Coatings Application

ASTM D6386 - 10 Standard Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting

Protective Coating User's Handbook, Second Edition, Published by NACE

It is a measure of force per unit area, defined as one newton per square metre.

Corrosion rate: 20 Microns Per Year

Severe marine environments such as this ocean front site may have zinc corrosion rates of around 20 microns or more per year. In this environment, the galvanized coating on the guardrail has a predicted life of 3-5 years.

ZINC CORROSION MECHANISMS

In the hierarchy of metals, zinc is relatively reactive, but like aluminium, relies on oxide films that develop on its surface to provide its superior corrosion resistance in atmospheric environments. Zinc is also an amphoteric metal, in that it reacts with both acids and alkalis.

AS/NZS 2699, on the other hand, uses an R0, R1, R2, R3, R4 and R5 rating criteria that is based on airborne salt (chloride) deposition.

The draft standard – AS 4312 Corrosivity zones in Australia, uses a C1,C2, C3, C4 and C5 rating system that is consistent with the system used in International (ISO) standards, specifically ISO 9223.

Food contactFood contactSince IRONOR® is free of toxic ingredients, it is extremely useful for nonpoisonous finishes applied to food processing plants such as sugar refineries, dairy plants, breweries and distilleries.

Series 1

Series 2

Series 3

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Category1

Category2

Category3

Category4

Series 1

Series 2

Series 3

Category Short term Long term (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

TYPICAL COATING WEIGHT (British Standards 729:1971)Category Min Ave coating weight (g/m2)

Min Ave coating Thickness (Micron) steel

articles > 5mm 610 85 (not centrifuged) <.

5mm 460 64 > 2 mm 335 47 Malleable casting

610 85 Threaded items 305 43 (centrifuged)

Visual Assesment of CorrosionASTM D610 - 08(2012)

SSPC-VIS 3

Guide and Reference Photographs for Steel Surfaces Prepared by Hand and Power Tool Cleaning

SSPC-VIS 2

Standard Method of Evaluating Degree of Rusting on Painted Steel Surfaces