Presented by: Tony Serdenes, Greenman-Pedersen

Maintenance Coating- Spot Repair and Primer as an Alternative to Full Coating Removal

Learning Outcomes• At the end of this webinar, you will be

able to:– Recognize the proper steps to take when

developing a maintenance coating plan– Determine when to perform spot repair,

spot repair and overcoating or complete recoat of structure

Introduction• The webinar will define maintenance painting

and explain the differences between repairing by overcoating versus full coating removal and recoat. Overcoating is generally defined as the practice of painting over an existing coating as a means of extending its useful service life. Overcoating may be a cost-effective alternative to complete coating removal and repainting.

Major Steps in Maintenance Coating• Six major steps in a maintenance coating

program:Step 1: Plan and conduct condition assessment

surveyStep 2: List potential maintenance painting

optionsStep 3: Select appropriate maintenance

painting optionsStep 4: Establish implementation proceduresStep 5: Implement maintenance painting

optionsStep 6: Plan and implement follow-up activities

Step 1• Used for several purposes:

– To determine the need for recoating– To determine the extent of corrosion

and corrosion damage– To determine the performance of

various coating systems– To prioritize coating requirements

where insufficient funds are available to do all the desired work

Step 1• Three types of

surveys:– General

Overview– Detailed Visual

Survey– Physical

Coating/Structural Inspection

General Overview• During a general coating condition

assessment:– Only one or two parameters are rated

(e.g., general condition or rusting)– Structure normally observed from the

ground– A qualitative rating – Done in a few hours or less

Detailed Visual Survey• During a detailed visual

assessment:– Relies exclusively on

visual observations– Numerous structural

elements are separately rated according to SSPC-VIS 2, ASTM D610 or equivalent

– Obtain a semi-quantitative rating of the percent of surface deteriorated

– May be used to develop preliminary cost estimates for recoating

Examples of Pictorial Guides

Physical Inspection• Physical testing is

required to determine whether the coating can be overcoated or repaired, or whether it is too weak to accept another coating layer

Physical Inspection• A physical inspection of the

structure and aged coating system should be conducted to determine:– Film thickness– Number of layers of paint– Adhesion– Underlying substrate condition– Coating type– Presence of soluble salt contamination

Physical Inspection• SSPC TU-3, Overcoating provides

discussion of the value of physical testing, as well as the procedures for testing

• Table 1 in Appendix A.1 contains a table assessing the risk of overcoating based on film thickness and adhesion of the existing coating

SSPC TU-3, Table 1

Structural Inspection• Coating

assessment should be included as part of any general structural inspection for loss of:– Metal– Broken joints

Structural Inspection• Evaluate and record the ratings of

individual structures or structural elements

• Create a sub unit sampling plan, identifying the portions of the structure or facility that will be rated and the type of rating scheme to be used

Step 2• List potential

maintenance painting options:– Spot repair only– Spot repair and

overcoating– Complete recoat

of structure

Spot Repair Only• Surface preparation and touch-up

coating of localized areas of deteriorated coating and corrosion

• Primarily a “stop-gap” method– Re-evaluate within 3 to 5 years

Spot Repair Only• Reasons why spot repair may be

selected are:– Repair are hidden or in a low-visibility

area– Corrosion and degradation are limited

to isolated areas• Less than 1% of total area

Spot Repair And Overcoating• Involves spot repair of deteriorated

coating and corroded areas followed by the application of a full finish coating over the entire surface, including spot repaired areas and intact coating areas

• Expected to give 5 years or more additional life

Complete Recoat of Structure• When corrosion and deterioration

exceed 16% of the total area

Determining Maintenance Painting Options

Step 3• Evaluate economics of available

options

• The variables involved in protective coatings often require a variety of solutions, each of which will carry unique cost-benefit factors

Step 3• Economic Analysis

– Initial Vs. Service Life Costs– Initial Cost Factors– Time Value of Money– Analysis

Step 3• Initial cost factors are:

– Mobilization/Demobilization– Access– Preparation– Material Costs

• Container Vs. Coverage• Service life of coatings• Initial Vs. Service life per square foot

Step 3• Example of Container

Vs. Coverage Calculation– Urethane finish @ 2

mils– Coating A at $30 per

gallon and 42% volume solids

– Coating B at $35 per gallon and 56% volume solids

Step 3• Calculate coverage and assume 20% loss

factor:

• 1604 X % Volume Solids X (1- Loss Factor) / DFT

• Cost analysis of paint material should be based on coverage cost NOT cost per gallon

Step 3• Coating A

– 1604 X 0.42 X 0.74 / 2 = 252.63 square feet

– $30 / 252.663 = $0.119 per square feet

• Coating B– 1604 X 0.56 X 0.75 / 2 = 336.84 square

feet– $35 / 336.84 = $0.1039 per square feet

Step 3• Initial cost factors

– Surface preparation– Application– Equipment– Curing / drying– Interference / downtime– Environmental / health / safety– Indirect

Step 3• Net Present Value

– The value today of a future payment or series of payments discounted at the appropriate discount rate

• Discounting– The process of finding the present value of a payment or

series of future cash flows; the reverse of compounding

• Net Future Value– The amount to which a payment or series of payments

will grow over a given future time period when compounded at a given interest rate

• Compounding– The arithmetic process of determining the final value of a

payment or series of payment when compound interest is applied

Step 3• Economic Analysis

– Projected life of structure– Consider systems

• Original painting• Touch-up (Spot/Spot)• Touch-up (Spot/Full)• Full repainting

– Cost calculations• Current cost levels• Net future levels• Net present levels• Average equivalent annual cost

Step 4• Select appropriate maintenance

painting options and establish implementation procedures– Identify relevant factors for coating

system selection– Select surface preparation methods

and coating materials – Prepare specification

Identify Relevant Factors for Coating System Selection• Coating system selection is

influenced by special factors such as:– Environmental, health and safety

regulations– Budgets– Exposure environments– Weather– Configuration of structure– Surface contaminants

Select Surface Preparation Method• Solvent cleaning• Hand and power tool cleaning• Abrasive blast cleaning• Wet abrasive blast cleaning• Waterjetting

Select Coating Materials• The selection of the coating system

involves two phases:– Identify the generic types– Identify the criteria for selecting

materials

Prepare Specification• Provides a

complete description of the desired work by prescribing specific procedures, processes and materials

• Provides criteria for acceptance or rejection of work

Step 5• Implement maintenance painting

options– Clean and coat the structure

Step 6• Plan and implement follow-up

activities:– Establish need for periodic inspection– Establish schedules for condition

assessment– Ensure proper documentation and filing

of historical information– Institute preventative maintenance

measures

Establish Need For Periodic Inspection• Inspection should be made of the

structure within 6 to 12 months after application

Establish Schedules For Condition Assessment• First condition assessment would

normally be conducted about 5 years after the original application and every 3 years thereafter

Ensure Proper Documentation And Filing Of Historical Information• Records of the daily inspection logs

and coatings should be stored in owners files

• Retained coating samples should be properly labeled and stored for at least 3 years

Institute Preventative Maintenance• Regular removal of contaminants

Summary• Following a maintenance coating

program enables the coating to perform its expected life and avoid early coating failure. At times when repair of the coating is needed an evaluation of the condition of the coating shall be performed to aid in determining the method of repair. Often spot repair or spot repair and overcoating is an economical alternative to full removal and recoat.