Calculating Coating Lifetime Costs

Presented by:Jayson L. Helsel, P.E.

KTA-Tator, Inc.

Learning Outcomes

• Completion of this webinar will enable the participant to: Define various service environments Identify suitable coating systems for intended service Describe a typical maintenance painting sequence Calculate installed cost for coating systems Perform economic analysis Calculate coating lifetime cost

History• Based on “Expected Service Life and Cost

Considerations for Maintenance and New Construction Protective Coating Work,” presented at NACE Corrosion 2008

• Data from survey of contractors and coating manufacturers

• Data presented in SSPC Painting Manual Volume 1, Good Painting Practice, Chapter 10.2, “Comparative Painting Costs”

Coating System Data

• Commonly used coating systems For typical service environments

• Service life estimates Time until 5-10% coating breakdown For practical maintenance sequence

• Current material costs• Current shop painting costs• Current field painting costs

Coating Systems - Atmospheric

• Most common systems for atmospheric exposure

• Surface preparation requirementBlast cleaning or hand/power tool

cleaning

• Minimum dry film thickness• Service environments

Coating Systems - Atmospheric

• Service environments per ISO 12944-2, “Classification of Environments”C2: Low C3: Medium C5-I: Very High, Industry C5-M: Very High, Marine

Coating Systems - Atmospheric

• Service environment definition

C2: Low

“Atmospheres with low levels of pollution; mostly rural areas”

Coating Systems - Atmospheric• Service environment definition

C3: Medium“Urban and industrial atmospheres, moderate sulfur dioxide pollution; coastal areas with low salinity”

“Production rooms with high humidity and some air pollution (e.g., food processing plants, laundries, breweries, dairies)”

Coating Systems - Atmospheric• Service environment definition

C5-I: Very High, Industry

“Industrial areas with high humidity and aggressive atmosphere”

Coating Systems - Atmospheric

• Service environment definition

C5-M: Very High, Marine

“Coastal and offshore areas with high salinity”

Coating Systems - Immersion

• Most common systems for immersion service

• Surface preparation requirementAbrasive blast cleaning

• Minimum dry film thickness• Service environments

Coating Systems - Immersion

• Service environments Potable water Fresh waterSalt water

Hot Dip Galvanizing• Service life for 4 mils minimum

(American Galvanizers Association)Mild (rural) = 68 Years Moderate (industrial) = 33 Years Severe (heavy industrial) = 21 Years

Practical Service Life

• Time until 5 to 10% coating breakdown occurs (SSPC-Vis 2 Rust Grade 4)

• Active rusting of the substrate is evident

Rust Grade 4 & 5 – General Rusting

Rust Grade 4 & 5 – Spot Rusting

Rust Grade 4 & 5 – Pinpoint Rusting

Typical Maintenance Painting Sequence

• Original Painting• Spot Touch-Up and Repair• Maintenance Repaint

Spot prime and full overcoat

• Full RepaintTotal coating removal and replacement

Typical Maintenance Painting Sequence

• Spot Touch-Up and RepairThe first time coating repairs are made Intended to be completed at the

“Practical Life” (from Tables 1A or 1B)

Typical Maintenance Painting Sequence

• Maintenance RepaintEstimated to be the “Practical Life” plus

33% • e.g. “P” x 1.33

Typical Maintenance Painting Sequence

• Full RepaintExpected to occur at the year of

“Maintenance Repaint” plus 50% of the “Practical Life” • e.g. Maintenance Repaint year + [“P” x 0.5]

Maintenance Painting Example

• Service Environment: C3• Surface Preparation: Abrasive Blast

Cleaning• Coating system: 2 coat epoxy • “P” life = 12 years

Spot touch up @ 12 yearsMaintenance repaint @ 16 yearsFull repaint @ 22 years

Cost Data

• Current material costs• Current shop painting costs• Current field painting costs

Cost Data

• Current material costsDFTTheoretical cost per sq ftPractical sprayPractical brush/roller

Cost Data

• Current shop painting costsSurface prep cost per sq ftPaint application cost per sq ftHot dip galvanizing costCost multipliers

• Size of job• Member size for galvanizing

Cost Data

• Current field painting costsSurface prep cost per sq ftPaint application cost per sq ftCost multipliers

• Size of job• Complexity of structure• Existing conditions

Cost Comparisons

• Shop vs. FieldShop abrasive blast cleaning and

priming approximately half of field cost (minimum of 250 tons of steel)

Cost Comparisons

Cost Comparisons

Cost Comparisons • Shop applied inorganic zinc vs. hot

dipped galvanizing75,000 to 125,000 sq ft steelModerate service environment (C3)35 year structure life4% inflation & 7% interest

• Initial cost of galvanizing 43% greater• Life cycle cost for galvanizing 15%

less

Economic Analysis

• Net Future Value (NFV)How much will it cost, in inflated dollars

in the year scheduled?NFV = Current Cost [(1 + i)n]

i = inflation, n = years

Economic Analysis

• Net Present Value (NPV)The present worth of the inflated cost (in

monies today invested at current interest rates)

NPV = NFV (1/ [(1 + i)n] )i = interest, n = years

Economic Analysis

• For each coating system:Timing and number of painting

operationsCost of each painting operations Carry out for projected life of structure

Economic Analysis

• Present value analysisFor each painting operation calculate:

• Current cost• Net future value• Net present value

Present Value Analysis

Economic Analysis

• Average Equivalent Annual Cost (AEAC)Converts entire stream of present and

future costs to a present worth (NPV)Distributes that sum in equal annual

amounts over the structure’s lifeRepresents coating lifetime or life cycle cost

i = interest, n = structure life

Life Cycle Cost

Life Cycle Cost

Summary

• Coating system selectionSurface preparation and service

environmentDetermines “Practical” life

• Material costs• Shop or field preparation and

application• Economic analysis• Life cycle cost