Cost vs. Performance: How Sustainable Coatings Maximize an Asset's Life Cycle

Sustainable coatings on a steel water storage tank exterior.

Sustainability. It's a concept that's been around for years, but now it's become the latest buzzword. You don't need to look far to find countless statements on what a sustainable future looks like, along with ways that both companies and individuals alike can better chart that path.

The water and wastewater industry is no exception, with sustainability emerging as one of the primary discussion points in many circles. The American Water Works Association (AWWA) even addresses the topic in its AWWA Asset Management Definitions Guidebook, asserting that sustainability truly focuses on the life cycle and service life of assets.

So, what does this have to do with protective coatings and linings? Before answering this question, I encourage you to first consider the topic of asset management. In Asset Management for Water and Wastewater Utilities, the EPA defines asset management as "the practice of managing infrastructure capital assets to minimize the total cost of owning and operating these assets while delivering the desired service levels." In other words, asset management is a systematic approach to maximizing the value of an asset in the most cost-effective manner throughout its entire life cycle.

There are many innovative products and systems to choose from in the world of protective coatings and linings. Looking at all of the options, one can expect to find a wide distribution of unique attributes, pros and cons, and, more importantly, asset life cycles. As a water and wastewater asset owner, how can you distinguish between these options? Furthermore, why does it matter?

You can use the same evaluation process regardless of the industry or asset within a nation's infrastructure to answer these questions. Using the water and wastewater industry as an example, let’s look at a scenario that involves a municipal water works department considering industrial coating options for a steel water storage tank in its community. To kickstart this conversation, here are a few resources that a design engineer—or, in our scenario, an asset owner—may find helpful in the evaluation process:

ISO 12944 – Corrosion Protection of Steel Structures

The ISO 12944 Standard for Corrosion Protection of Steel Structures describes different types of paint and paint systems that are used to protect against the corrosion of steel structures. One valuable part of this guide is the breakdown of the various atmospheric service environments that structures often face. When evaluating different coating systems, you can reference this guide to take into account the specific atmospheric environment of the asset's location.

AWWA D102 – Coating Steel Water-Storage Tanks

A committee comprised of industry experts across various roles within the water and wastewater industry created the AWWA D102 Standard for Coating Steel Water-Storage Tanks. Among other guidance, this standard lays out some generic outside coating systems (OCS) and inside coating systems (ICS) as coating and lining considerations for steel water-storage tanks.

NACE Paper No. 10673 – Protective Coating Service Life & Cost Considerations

The NACE Paper No. 10673: Expected Service Life & Cost Considerations for Maintenance/New Construction Protective Coating Work is especially beneficial to those striving to identify the estimated costs and approximate service lives of various coating and lining systems. As a reference point, below are two tables taken from this paper.

One lists an assortment of atmospheric coating systems, while the other highlights several commonly used systems for immersion service. Some of the atmospheric service levels referenced in this paper refer to ISO 12944. It also names the various outside and inside coating systems listed in AWWA D102 (designated by OCS and ICS).

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

System No.TypeCoating Systems for Atmospheric Exposure (primer/midcoat/topcoat)Surface PreparationNumber of CoatsDFT Minimum (mils)Practical Maintenance Time
Mild (rural)/C2Moderate (industrial)/C3Severe (heavy industrial)/C5-ISeacoast Heavy Industrial/C5-M
1 Acrylic Acrylic Waterborne/Acrylic WB/Acrylic WB Hand/Power 3 6 12 8 5 5
2 Acrylic Acrylic Waterborne/Acrylic WB/Acrylic WB Blast 3 6 17 12 8 8
3 Alkyd Alkyd/Alkyd/Alkyd Hand/Power 3 6 12 8 5 5
4 Alkyd Alkyd/Alkyd/Alkyd (AWWA OCS-1C) Blast 3 6 17 12 8 8
5 Alkyd Alkyd/Alkyd/Urethane Alkyd Blast 3 6 18 13 9 9
6 Alkyd Alkyd/Alkyd/Silicone Alkyd (AWWA OCS-1D) Blast 3 6 20 14 10 10
7 Epoxy Surface Tolerant Epoxy (STE) Hand/Power 1 5 11 6 4 4
8 Epoxy Surface Tolerant Epoxy/STE Hand/Power 2 10 17 12 9 9
9 Epoxy Surface Tolerant Epoxy/STE Blast 2 10 21 15 12 12
10 Epoxy Surface Tolerant Epoxy/Polyurethane Hand/Power 2 7 17 12 9 9
11 Epoxy Surface Tolerant Epoxy/Polyurethane Blast 2 7 21 15 12 12
12 Epoxy Surf-Tolerant Epoxy/STE/Polyurethane Hand/Power 3 12 21 15 12 12
13 Epoxy Surf-Tolerant Epoxy/STE/Polyurethane Blast 3 12 24 18 14 14
14 Epoxy Epoxy 100% Sol Pent Sealer/Epoxy Hand/Power 2 6 13 8 5 5
15 Epoxy Epoxy 100% Solids Penetrating Sealer/Polyurethane Hand/Power 2 4 12 7 4 4
16 Epoxy Epoxy 100% Solids Penetrating Sealer/Epoxy/Polyurethane Hand/Power 3 8 17 12 9 9
17 Epoxy Epoxy/Epoxy Blast 2 8 20 14 11 11
18 Epoxy Epoxy/Epoxy/Epoxy Blast 3 12 23 17 14 14
19 Epoxy Epoxy/Polyurethane Blast 2 6 20 14 11 11
20 Epoxy Epoxy/Polysiloxane Blast 2 9 22 16 12 12
21 Epoxy Epoxy/Epoxy/Polyurethane (AWWA OCS-5) Blast 3 10 23 17 13 13
22 Epoxy Epoxy Waterborne/Epoxy WB/Epoxy WB Blast 3 9 20 14 11 11
23 Epoxy Epoxy Waterborne/Epoxy WB/Polyurethane WB (AWWA OCS-7) Blast 3 9 21 15 12 12
24 Epoxy Zinc Epoxy Zinc/Epoxy Blast 2 7 24 17 11 11
25 Epoxy Zinc Epoxy Zinc/Epoxy/Epoxy Blast 3 11 29 20 14 14
26 Epoxy Zinc Epoxy Zinc/Polyurethane Blast 2 6 24 17 11 11
27 Epoxy Zinc Epoxy Zinc/Epoxy/Polyurethane Blast 3 10 29 20 14 14
28 Epoxy Zinc Epoxy Zinc/Epoxy/Fluorinated Polyurethane Blast 3 10 34 24 18 18
29 Organic Zinc Organic Zinc/Acrylic Waterborne/Acrylic WB (AWWA OCS-3) Blast 3 7 21 15 11 11
30 Organic Zinc Organic Zinc/Epoxy/Polyurethane (AWWA OCS-6) Blast 3 10 26 18 13 13
31 Organic Zinc Organic Zinc/Polysiloxane Blast 2 8 29 19 14 14
32 Organic Zinc Organic Zinc/Epoxy/Polysiloxane Blast 3 12 30 21 15 15
33 Organic Zinc Organic Zinc/Polyaspartic Blast 2 8 26 18 13 13

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

Coating System No.TypeCoating Systems for Immersion Service (primer/midcoat/topcoat)Surface PreparationNumber of CoatsDFT Minimum (mils)Practical Maintenance Time
Potable WaterFresh Water ImmersionSalt Water Immersion
1b Epoxy Coal Tar Epoxy Blast 2 16 - 17 14
2b Epoxy Epoxy/Epoxy Blast 2 8 12 9 8
3b Epoxy Epoxy/Epoxy (AWWA ICS-1) Blast 2 6 10 8 6
4b Epoxy Epoxy/Epoxy/Epoxy (AWWA ICS-2) Blast 3 12 15 12 11
5b Epoxy Epoxy 100% Solids (AWWA ICS-3) Blast 1 20 18 16 14
6b Organic Zinc/Epoxy Organic Zinc/Epoxy/Epoxy (AWWA ICS-5) Blast 3 10 16 13 12
7b Epoxy Phenolic Epoxy Phenolic/Epoxy Phenolic Blast 2 12 - 14 12
8b Metallizing Metallizing/Epoxy Blast 2 9 20 17 15
9b Metallizing Metallizing/Epoxy/Epoxy Blast 3 13 24 20 18
10b Misc Polyurethane 100% Solids (AWWA ICS-4) Blast 1 25 18 16 14
11b Misc Vinyl Ester/Vinyl Ester Blast 2 20 - 14 12
12b Misc Polyester (composite filled) Blast 2 25 - 14 12
13b Misc Polyurea Blast 1 25 18 16 14

Looking back at our original scenario, what does the municipal water works department do with this information? At the end of the day, while price is certainly important, these resources demonstrate that it should not be the sole deciding factor.

To take this even further, consider what is involved in coating and lining a water-storage tank. With whatever system(s) you choose, you will likely incur a standard set of associated costs—ranging from abrasive blasting, containment and rigging, to equipment and other mobilization costs. In addition, it’s also crucial to consider the additional costs that impact the surrounding community, such as traffic disruption or environmental impacts.

For example, according to NACE Paper No. 10673, an organic zinc-epoxy-polysiloxane coating system (over a blasted steel surface) has an expected service life of 21 years in a moderate environment. When comparing this to many of the other listed systems, one can assume that this system will require fewer repaints—thus reducing the other associated disruptions and environmental impacts.

Since several coating systems contain the previously mentioned standard costs, evaluating these systems on more than their price per gallon is essential. Instead, you should heavily weigh the expected service lives of each coating system, along with their associated costs, to fully realize fiscal sustainability.

In its International Good Practice Principles for Sustainable Infrastructure manual, the United Nations discusses how "sustainable options may have higher up-front costs but (they) deliver significant savings and benefits in the long run."One can argue that this same premise is true when evaluating the various coating and lining system options available in the marketplace.

Looking at this from a holistic viewpoint, it is not far-fetched to describe materials and systems with longer service lives as the more sustainable options. With more infrastructure funding on the horizon, it will be imperative for water and wastewater asset owners to utilize these finances in the best way possible. Developing a framework and using some of these available resources will better equip decision-maker(s) to choose coatings that deliver the most sustainable, long-term solutions.

Want to Explore Protective Coatings and Linings in the Water & Wastewater Industry?

Check out Carboline's Water/Wastewater Asset Protection Guide, which offers an interactive, step-by-step look at the drinking water treatment, transmission and storage phases, as well as the wastewater collection and treatment process. It outlines each asset and provides coating and lining recommendations for each substrate within the structure.