service life

Expected Service Life and Cost Considerations for Maintenance and New Construction Protective Coating Work

Designed to assist the coatings engineer or specifier in identifying candidate protective coating systems for specific service environments applicable to a broad array of industries, this guide provides the following.

  • Commonly used generic coating systems.
  • Service life for each in specific environments.
  • Current material costs.
  • Current field and shop painting costs.
  • Guidelines for calculating approximate installed costs of the systems.

Guidelines for developing long-term life-cycle costs and number of paintings for the expected life of the structure are also included. The basic elements of economic analysis and justification are addressed together with guidance on the preparation of a Present Value Analysis. Examples are provided to aid the reader in the proper use of the information (Tables 1-3).

Table 1: Examples Using Practical Maintenance Sequence: System with 20-Year Practical Life
and Original Shop-Installed Cost of $4.10 per Square Foot, and with 20-year Practical Life and Original Field-Installed Cost of $5.11 per Square Foot.

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Table 2: Example of Present Value Analysis: Total Painting Cost per Sqare Foot for 45-Year Plant Life, Field Application Three-Coat Epoxy Zinc/Epoxy/Polyurethane, Blast-Cleaning, 14-Year System Life (Severe/C5-I).

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Table 3: Example of Economic Analysis: Total Painting Cost per Sqare Foot for 35-Year Structure Life, Moderate (C3) Environment One-Coat Inorganic Zinc System, Shop-Automated Blast-Cleaning
17-Year “P” Life, Inflation = 4%, Interest = 7%

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INTRODUCTION

Major manufacturers of protective coatings, steel fabricators, painting contractors, galvanizers and end users were surveyed to identify surface preparation and coating application costs, coating material costs, typical industrial environments and available generic coatings for use within those environments, and expected coating service lives.

The approach to this cost data is meant to be practical. Instead of burdening the coating engineer with complicated cost formulas based on hourly wages, supervision, equipment rates, overhead, profit and other cost elements, this guide provides total unit costs, which include all of these elements. The costs are intended to reflect current, competitive/commercial prices charged in today’s market.

Surface preparation and application costs are primarily based on data from major steel fabricators and painting contractors. Material costs are provided by major suppliers who furnished approximate prices at which coatings are being sold on commercial-sized jobs. The current cost data was developed from the collected data along with common industry cost references.

This guide produces a base cost of painting steel on the ground at the site that is then adjusted to an installed cost, using multipliers based on input from painting contractors. Most elements used in the guide have come from these contractors and have proven to be practical over the guide’s long history.

Limitations

The costs in the guide are not intended to be absolute, nor are they intended for use in estimating or negotiating. Specific job costs will vary depending on the job size, geographic location, logistics, competitive climate and other factors, including available working hours, allowable time to completion, traffic restrictions and level of inspection required.

The purpose of the guide is to provide an easy-to-use, practical means to identify, compare, select and justify suitable, cost-effective protective coating systems for specific environments, and to answer fundamental questions such as the following.

  • What systems might work?
  • What are the relative installed costs?
  • Comparatively, how long will the systems last?
  • What are the relative costs per year per square foot?

ANALYSIS: SYSTEM CHANGES, UPDATES, SERVICE ENVIRONMENT AND PRODUCT TRENDS

Coating System Update

The information detailed for designated “coating systems” includes the level of surface preparation, generic coating type(s) and a minimum coating dry-film thickness.

The categories for surface preparation include either hand/power tool cleaning or abrasive blast-cleaning. A distinction is not made between grades of blast-cleaning (for example, Near-White versus Commercial Blast).

The coating systems are divided into two categories: those for atmospheric exposure listed in Table 4A and those for immersion (water) service listed in Table 4B. Tables 4A and 4B list the expected service life (as subsequently defined) for each “coating system” corresponding to particular service environments as described below.

Table 4A: Estimated Service Life for Practical Maintenance Coating Systems for Atmospheric Exposure (in years before first maintenance painting)1

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Table 4B: Estimated Service Life for Practical Maintenance Coating Systems for Immersion Service (in years before first maintenance painting)1

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SERVICE ENVIRONMENT

The “service environment” defines the anticipated environmental exposure conditions for a coating system. For atmospheric exposure, there are four service environments that correspond to ISO1 12944-2, “Classification of Environments.” These categories are defined as follows.

  • C2: Low – Atmospheres with low levels of pollution; mostly rural areas.
  • C3: Medium – Urban and industrial atmospheres, moderate sulfur dioxide pollution; coastal areas with low salinity.
  • C5-I: Very High, Industry – Industrial areas with high humidity and aggres-
  • sive atmosphere.
  • C5-M: Very High, Marine – Coastal and offshore areas with high salinity.

For water immersion service, there are three service environments corresponding to exposure to potable water, fresh water and salt water.

Hot Dip Galvanizing

Hot dip galvanizing is a shop-applied coating (installed by dipping the parts in special cleaning and molten zinc baths), which provides a combination of physical properties that can be superior to many other coating systems. A galvanized coating consists of a progression of zinc-iron alloy layers metallurgically bonded to steel substrates. The resulting coating is anodic to steel, resists underfilm corrosion, has excellent abrasion resistance and provides excellent film build at sharp corners, edges and projections. The service life, material costs and all labor and equipment costs associated with surface preparation, fluxing, dipping and cooling for hot dip galvanizing are included in Tables 4A and 6.

Table 5: Typical Material Costs of Paints and Protective Coatings Approximate Cost per Square Foot at
Typical DFT

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Table 6: Shop Painting Costs per Square Foot Including Labor, Equipment and Related Costs1 (No Material Costs Included)

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Size of Job Multipliers (per square foot)

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Conversion of Tons of Steel to Square Feet

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Member Size Multipliers for Hot Dip Galvanizing3 Member Weight Per Foot (lbs./ft.)

Table 7: Field Painting Costs per Square Foot Including Labor, Equipment and Related Costs1 (No Material Costs Included)

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Metallizing Systems

Metallizing is the application of zinc and/or aluminum directly to a steel surface. For atmospheric exposure, a typical composition of the metal is 85-percent zinc and 15-percent aluminum. The metal is applied by “thermal spray” where the metal, in wire or powder form, is heated, liquefied and sprayed onto the substrate. A sealer coat is often applied to the metal coating since metallizing results in a somewhat porous coating layer. Metallizing provides galvanic protection to the steel and is a very durable and abrasion-resistant coating. This system’s performance (life) is provided in Tables 4A and 4B. The costs for metallizing are estimates based on information published by the Federal Highway Administration.2,3

Paint Removal

The Containment Multiplier Guidelines in Table 8 are included to aid in developing approximate costs for paint removal depending upon the containment type. These are to be used in conjunction with surface preparation costs developed in Table 7. The containment type (class) is based on SSPC4 Guide No. 6, “Guide for Containing Debris Generated During Paint Removal Operations.”

Table 8: Paint Removal Containment Multipliers Guidelines Containment Designation is in accordance with SSPC Technology Guide No. 6, Guide for Containing Surface Preparation Debris Generated During Paint Removal Operations

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Maintenance Painting Sequences

This guide presents a sequence for typical maintenance painting as follows.

  • Original painting.
  • Spot touch-up and repair.
  • Maintenance repaint (spot prime and full coat).
  • Full repaint.

Examples of maintenance painting following this convention for various coating systems are presented in the guide. It is important to note, however, that this sequence does not always represent the most economical approach to maintenance painting. Often, several cycles of touch-up and maintenance repainting can be performed prior to the need for full repainting. The determining factors involved with this type of extended maintenance painting sequence are the amount of corrosion present and the physical characteristics of the existing coatings. These factors should be investigated prior to the next scheduled painting operation.

Decisions involving whether a full repaint is required, as opposed to a maintenance repaint or touch-up, should be based on the results of a field investigation. Generally, touch-up procedures are used when the amount of corrosion is limited or found in discrete areas. The success of maintenance repainting depends on the coating type, thickness and adhesion of the existing coating system, as well as the substrate condition.

The general procedures outlined in this guide may be used to determine installed costs and life-cycle costs for any combination of maintenance painting sequences. Table 9 can be used as a guide to determine maintenance repainting risk (that is, whether the existing coating system might be a candidate for repair).

Table 9: Determination of Maintenance Repainting Risk for Alkyd Coatings1

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Worksheets (Shop And Field Application)

Worksheets were developed by the authors to aid in preparing initial installation costs but could not be included due to space limitations. The worksheets are available upon request.

PRACTICAL SERVICE LIFE

How long a coating system will last depends on the user’s approach to, and philosophy of, maintenance painting. Is protection alone important or is appearance also a primary consideration? Is painting viewed as an unfortunate necessity or is cost-effective corrosion protection the objective?

This guide supplies system life estimates for a “practical” maintenance approach. The estimated service life is not the time a coating system should need to be replaced but, rather, the time the maintenance painting sequence should begin — when there is 5- to 10-percent coating breakdown (SSPC-Vis 2 Rust Grade 4), and active rusting of the substrate is present.

It should be noted, however, that the distribution of the breakdown must also be considered when making judgments regarding the feasibility and costs of maintenance painting. For example, a 5-percent breakdown that occurs in well-defined areas can be practically repaired through localized touch-up, whereas a 5-percent breakdown uniformly scattered across 100 percent of the surface may be beyond practical spot repair. At a minimum, a full coat is required, if the coating is even salvageable. The guide does not address these differences, but the user must take them into consideration when making painting decisions and determining the costs of painting.

Note that this “practical” maintenance sequence is based on one approach, but it may not always represent the most economical approach to maintenance painting. The determining factors are the amount of corrosion present and the physical characteristics of the existing coatings. These factors should be assessed prior to the next scheduled painting operation. In some cases, multiple cycles of touch-up and maintenance repainting can be performed, pushing the need for full repainting further into the future.

Decisions involving whether a full repaint is required, as opposed to another maintenance repaint or touch-up, should be based on the results of an investigation of coating thickness, adhesion, substrate condition, and the extent and distribution of corrosion.

TYPICAL MAINTENANCE PAINTING PRACTICES

The sequences followed by users in maintenance painting vary widely. For some, the only criterion is this question: “Does it need to be painted?” However, when reviewing the subject with quality painting contractors, the consensus is that most users generally follow this sequence.

  • Original painting.
  • Spot touch-up and repair.
  • Maintenance repaint (spot prime and full coat).
  • Full repaint (total coating removal and replacement).

“Spot touch-up and repair,” which is the first time coating repairs are made, is intended to be completed at the “Practical Life” of the coating system as listed in Tables 4A and 4B.

The time until “Maintenance Repaint,” which includes spot priming and a full overcoat, is estimated to be the Practical Life plus 33 percent (that is, P x 1.33).

A “Full Repaint,” involving total coating removal and replacement, is expected to occur at the year of “Maintenance Repaint” plus 50 percent of the “Practical Life” (that is, Maintenance Repaint year + [P x 0.5]).

For example, if the practical life of a system is 21 years, the spot touch-up would occur at year 21, with an overcoat at year 28 and full replacement of the system at year 39. Even though complete removal and replacement of a system is no longer a “maintenance” operation, it may be included in the life-cycle analysis (as subsequently discussed) to allow for a comparison of different coating systems that have varying lengths of practical service life.

The continuing cycle of maintenance painting is also necessary when the design life of the structure exceeds the design life of the coating system. In this case, the cost of complete coating replacement and additional maintenance cycles must be calculated to determine the total cost of the corrosion protective system over the entire life of the structure.

Note that the coating replacement and continued maintenance painting assumes the same type(s) of coatings for the particular protective coating system are used over time.

COST COMPARISONS

Shop Versus Field Painting – New Construction

Shop blasting and priming has a substantially lower cost as compared to doing the work in the field when a minimum of 250 tons of steel are involved and the steel fabricator has rotary wheel-blasting equipment (see Tables 6 and 7).

Field touch-up is necessary to repair in-transit damage, but cost savings are often enough to justify shop preparation and painting. Application is easier on the ground, spray loss is reduced and safety enhanced. Jobsite conflicts, scheduling difficulties and compromised applications that can be common on new projects are greatly reduced or eliminated.

Field touch-up, however, may lead to a spotty appearance and special handling procedures are necessary to protect the finish during shipping and erection. An alternate approach, when a spotted appearance due to touch-up is unacceptable, involves the application of all coats in the shop except the finish, which is applied in the field after erection.

Costs For Typical Maintenance Painting Practices

The life and cost of the repainting steps following typical maintenance painting practices will vary according to whether the original work was shop or field applied. Table 1 provides estimated costs for a typical maintenance painting sequence, based on both shop and field application for the original work. This table includes multipliers for determining the approximate cost for each field repainting step based on whether the original work involving all coats was done in the shop or field.

ECONOMIC ANALYSIS AND JUSTIFICATION

This subject is sometimes misunderstood and overly complicated for paint and coating systems. Capital items require intricate analyses to identify the full financial impact. Paint and coating systems are basically expense items without salvage value or depreciation considerations. However, they are tax-deductible in most instances. Only a few calculations are needed to compare one system with another and to measure each system’s true cost in comparable dollars.

For each system used or considered, list the timing, number and cost of painting operations required to protect the structure for its projected life. This should include such items as original painting, touch-up, touch-up and full coats, and full repainting. The cost of each painting operation should be calculated in three categories as shown in Table 2.

  1. At Current Cost levels.
  2. At Net Future Value (NFV) levels – that is, the current cost with inflation included. How much will it cost, in inflated dollars, in the year scheduled?
  3. At Net Present Value (NPV) levels – that is, the present worth of the inflated cost (NFV) in monies today invested at current interest rates.

For example, assuming 5-percent inflation, a current cost of $10 today inflates to $12.76 in five years.

$12.76 is the NFV. The formula2,3 for calculating this is (i = inflation; n = number of years).

NFV = Current Cost [ (1 + i)n ]

To calculate the NPV, or what $12.76 (NFV) is worth today if invested at current interest rates (10 percent) for five years, use the following formula2,3 (i = interest rate; n = number of years):

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Invested today at 10 percent for five years, $7.92 will yield $12.76.

By making these calculations for each of the candidate system’s painting operations, the true cost and number of painting operations can be compared, and the coating selection made on a comparable basis. One system may be less costly to install initially, but if it has a shorter life and requires more frequent repainting, the financial cost and impact of the additional repainting — and the disruption of the structure’s intended service or impact on others (for example, traffic disruption in the case of bridges) — must be recognized.

An additional calculation, called the Average Equivalent Annual Cost (AEAC), is popular with many engineers. This simply converts the entire stream of present and future costs to a present worth (NPV) and then distributes that sum in equal annual amounts over the structure’s life. The formula5,6 to calculate this is (i = interest; n = structure life).

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To summarize, the steps for calculating an economic analysis of a paint and coating system follow.

For each candidate system (using a separate sheet for each), develop a timetable for the design or projected life of the coating on the structure).

For each system, indicate in the timetable when all painting operations will take place: original painting, touch-up, maintenance repainting and full repainting. If the analysis is based on the design life of the structure, repeat the painting cycle(s) as necessary to achieve the desired life. Insert the current costs for these operations (that is, the costs if they were performed today).

Using the current inflation rate, calculate and record the NFV for each of the painting operations.

Using the current interest rate, calculate and record the NPV of the NFV for all the painting operations.

For each system, total the sum of the three categories (current cost, NFV and NPV).

Compare these values, particularly NPV, for a direct comparison of number of painting operations and each system’s true cost in monies today. See Table 2 for an example of a Present Value Analysis (PVA).

To compare the life-cycle costs for each system, calculate the AEAC. See Table 3 for an example.

On new capital projects, coating costs may be capitalized, which will require considerations for depreciation. However, most maintenance costs are tax-deductible, and when deducted, reduce the taxable income of the owner. The same PVA outlined in the example should be followed for making the coating selection and the analyses turned over to project management for further financial treatment and tax considerations.

GUIDE TO TABLES

This guide defines a wide variety of coating systems in terms of required surface preparation and generic coating product(s). In the tables 4A through 9, the practical service life of coating systems in atmospheric exposure is defined for four different standard service environments. The service life for coating systems in water immersion service is defined for three categories of water exposure. Service life data for metallizing and hot dip galvanizing is included.

Regulations on containment, capture and disposal of removed coatings (especially coatings containing hazardous metals) continue to impact the cost of painting projects and may not be captured by the estimates in this guide.

Surface preparation techniques that use water or non-traditional abrasives may adequately remove coatings and may reduce potential risks to the environment and the workers involved in coating removal.

CITATIONS

1.International Organization for Standardization, 1, ch. de la Voie-Creuse, CP 56 – CH-1211 Geneva 20, Switzerland.

2.Federal Highway Administration, Turner-Fairbank Highway Research Center, Bridge Coating Technology, “Metallizing: The Illinois Experience,” http://www.tfhrc.gov/hnr20/bridge/ill.htm.

3.Castler, L.B., “Rapid Deployment Technology a New Concept for Connecticut,” SSPC 2003 Technical Presentations.

4.SSPC: The Society for Protective Coatings, 800 Trumbull Drive, Pittsburgh, Pa. 15205.

5.Financial Compound Interest and Annuity Tables, Fifth Edition, Financial Publishing Co., NYC, Table 4, 1970.

6.D.E. White, P.A. Johnson, P.M. Charlton, “R-O-W Vegetarian Control: The Never-Ending Process,” Electrical World, p. 41, August 1986.

REFERENCES

J. Helsel, R. Lanterman and M. Reina, “Expected Service Life and Cost Considerations for Maintenance and New Construction Protective Coating Work,” CORROSION 2014, Paper No. 4088.

K. A. Trimber and D. P. Adley, Project Design – Industrial Lead Paint Removal Handbook, Volume II, Steel Structures Painting Council, SSPC 95-06, Chapter 2.

SSPC: The Society for Protective Coatings, Pittsburgh, Pa., Good Painting Practices, Volume 1.

National Association of Corrosion Engineers, Houston, Texas, TPC Publication 9, “User’s Guide to Hot Dip Galvanizing,” Appendix C.

ABOUT THE AUTHORS

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Jay Helsel

Jay Helsel is a senior consultant with KTA-Tator, Inc. He holds an Master of Science degree in chemical engineering from the University of Michigan, is a licensed professional engineer in multiple states, a NACE-certified Coating Inspector, and an SSPC-certified Protective Coatings Specialist (PCS) and Concrete Coatings Inspector (CCI). At KTA, Helsel manages coating projects, performs failure investigations and coating surveys, writes coating specifications and is a regular instructor for KTA coating inspection courses. Helsel previously served as a lieutenant commander in the U.S. Coast Guard with experience in marine vessel inspection.

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Rob Lanterman

Robert Lanterman is a coating consultant with KTA-Tator, Inc. He holds a Bachelor’s degree in chemical engineering from Youngstown State University, is an SSPC-certified Protective Coatings Specialist, an API 653 Certified Inspector and a NACE Level-3-certified Coating Inspector with Marine Endorsement. At KTA, Lanterman manages coating projects, performs failure investigations and coating surveys, and writes coating specifications.

Reproduced with permission from NACE International, Houston, Texas. All rights reserved. Authors Jayson L. Helsel, P.E. and Robert Lanterman, KTA-Tator Inc., Paper No. 7422 presented at CORROSION/2016, Vancouver, B.C. © NACE International 2016.

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