Maintenance Coating Spot Repair and Primer as an

Maintenance Coating- Spot Repair and Primer as an Alternative to Full Coating Removal Presented by: Tony Serdenes, Greenman. Pedersen

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 survey Step 2: List potential maintenance painting options Step 3: Select appropriate maintenance painting options Step 4: Establish implementation procedures Step 5: Implement maintenance painting options Step 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 SSPCVIS 2, ASTM D 610 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 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.