Overcoating paint systems on water tanks

1. Overcoating Water TanksOvercoating Water Tanks
Jim Skilton & Jeff White
Southern Corrosion & Induron Protective Coatings

2. OverCoating Paint Systems
on Water Tanks

3. We never know the worth of water till
the well is dry.
-English Proverb

4. 38% OF EXISTING INDUSTRIAL
STEEL HAS BEEN COATED WITH
LEAD-BASED PAINT INCLUDING
OVER 51,000 WATER TANKS.

5. Check Adhesion and Film
Integrity
• What is the total film thickness?
• How many coats of paint?
• How good is the adhesion to the substrate and
between coats?
• Are there film defects such as cracking or blistering?

7. Degree of Rusting
• ASTM D 610 Evaluating Degree of Rusting on
Painted Steel Surfaces
• Less Than 10% Rusting

9. • Clean, Dry & Free of Contaminants
• Power Washing with Detergent
• Spot Power Tool Cleaning
- SSPC-SP3
- SSPC-SP11
Surface Preparation for Overcoat
Systems

10. Surface Preparation for Overcoat
Systems

11. • Evaluate the Degree of Rusting
• Evaluate the Adhesion & Film Integrity
Determining the Condition of the
Existing Paint System

12. • The condition of the existing coating system
• The surface preparation prior to overcoating
• The geographic location (exposure conditions)
• The type of overcoat system selected
• Selecting a knowledgable, experienced contractor
• Owner expectations
Factors that Determine Overcoat
Success

13. Selecting a Successful
Overcoat System

14. DETERMINING THE
DELAMINATION RISK FACTOR
Delamination Risk Factor
The degree of risk associated with the existing coating system
delaminating between coats, or from the substrate after
application of an overcoat system taking into account
freeze/thaw cycling and total film thickness of the existing
system.

15. DELAMINATION RISK FACTOR
0 Poor 5 High 5+ 5++
1 - 4.5 - 5 5+
2 - 4 - 4.5 5
3 - 3 - 3.5 4
4 - 2 - 2.5 3
5 Excellent 1 Low 1.5 2
Adhesion
Results
Delamination
Risk Factor
(D.R.F.)
Delamination
Risk Factor w/
Freeze & Thaw
D.R.F. w/ Freeze &
Thaw Cycling
& High D.F.T.

16. COHESIVE STRESS FACTORS
Elastomeric Acrylic Emulsions 1 Low
Acrylic Emulsions 2 -
Medium to Long Oil Alkyds 3 -
Epoxy Mastics 4 -
Conventional 2-component 5 High
epoxies, aliphatic urethanes and
moisture-cured urethanes
Generic Type Cohesive Stress Factor

17. SELECTING CANDIDATE
OVERCOAT SYSTEMS
Delamination Risk Factor
5 None Recommended
4.5 None Recommended
4 1 or 2
3 1, 2, 3 or 4
2 1, 2, 3, 4 or 5
1 1, 2, 3, 4 or 5
Candiate Overcoat Systems
Based on Cohesive Stress Factors

18. Adhesion / Film Integrity
+
Geographic Location
+
Existing Film Thickness
DELAMINATION RISK FACTOR

19. Delamination Risk Factor
+
Cohesive Stress Factor
CANDIDATE OVERCOAT SYSTEM

20. Candidate Overcoat System
+
Test Patch Evaluation
SUCCESSFUL OVERCOAT SYSTEM

21. Excellence is not an act, but a habit
-Aristotle

22. Question? Comments? Discussions?