1. PAINT BASICS AND CORROSION IN METAL AIA103 Provider J476
Corrosion & Premature Coating Failures in Metal 1

2. Basic Composition of Paint
Solvents (Liquids)
Pigments
Additives
Resins (Binder) 2

3. Prime Pigments Titanium Dioxide (TiO2) Zinc Oxide
White
Titanium Dioxide (TiO2)
provides excellent hiding power and whiteness
available as a solid (powder) or liquid (slurry)
Zinc Oxide
controls mildew
resists ultra-violet light
resists yellowing
Titanium dioxide is the world's primary pigment for providing whiteness, brightness and opacity. 3

4. Resins Types: Latex, Alkyd, Epoxy, Polyurethane
Binds or glues ingredients (pigments and additives) of paint together
Resin provides adhesion to the substrate
Resin provides durability & resistance properties:
U-V resistance
Moisture resistance
Chemical resistance
Stain resistance
Fade resistance
Chalk resistance
Block resistance 4

5. Gloss/Sheen Levels
• Gloss or Sheen of paint refers to reflectivity or how shiny the dry paint film is.
There is lack of standards and confusion in the paint industry related to gloss or sheen levels.
• Gloss is measured at 60° for flat to gloss ranges.
Sheen is measures at 85° between flat to eggshell
• Some paint manufacturers use different terms to define products between flat and semi-gloss: silk, suede, satin, velvet, eggshell, low sheen, low luster, pearl, etc. 5

6. Gloss/Sheen Levels Term Gloss @ 60° Sheen @ 85 Flat 0-5 0-5
Velvet/Low Luster
Eggshell
Low Sheen
Semi-Gloss
Gloss 75+ 6

7. Alkyd Resin Technology
ALKYD (Oil-Based)
A synthetic resin made by reacting alcohols and fatty acids
Soya bean, linseed, tung-oil oil commonly used
Benefits of alkyds:
Superior brushing characteristics
Abrasion resistance
Excellent flow and leveling
Good adhesion
Used in rust preventative paint
Alkyds have limited availability and use in California. 7

8. Latex Resin Technology
LATEX (water-based)
Synthetic polymers
Main resins
100% Acrylic
Styrene Acrylic
Vinyl-Acrylic
Acrylic Copolymer
Vinyl Acetate Ethylene 8

9. Latex Resin Technology
QUALITY Latex paint benefits include:
* Ease of application * Low odor
* Yellowing resistance * Color retention
* Chalk resistance * Gloss retention
* Washability * Durability
* Good flow & leveling * Flexibility
* Excellent adhesion * Scrub resistance
* Improved adhesion * Water clean-up 9

10. Acrylic vs. Alkyd Paints
These paints have been exposed to the elements for 46 years. Over that time, the PVA (and the alkyd) paints have disintegrated.  The 100% acrylic paint remains in remarkably good shape.  The paint film is essentially intact, and, while it has chalked and faded, it retains its original green color.
Top left: Alkyd paint
Top right: Vinyl-Acrylic paint
Bottom left: Alkyd paint
Bottom right: 100% acrylic paint 10

11. Acrylic vs. Alkyd Paints
The paint on the left half of each board is acrylic, the paint on the right half, an alkyd.  The colors of the paints were identical when applied.  After 15 years of weathering, the appearance of the alkyds has changed dramatically.  All have lost gloss, faded, and chalked.  The acrylic paints, in contrast, have proven remarkably durable with good color retention. 11

12. Premature Coating Failure
DEFINITION:
The deterioration of the coating system, or corrosion of the coated surface, more rapidly than would normally be expected under the service conditions. 12

13. Corrosion
Simply put, corrosion is created when two dissimilar metals at atomic levels come into contact with each other and create a chemical reaction. The new compound is called oxide. In iron it is called Iron oxide. In aluminum, aluminum oxide and in copper, copper oxide.
These metals will not rust or corrode unless a conductor between the two metals or atoms is present.
Water or oxygen in contact with the metal for a longer period of time is normally the conductor that starts the rusting or corrosion process. Salts in the water will accelerate the process. 13

14. Galvanized Metal White Rust
Pure water (rain, dew, condensation) contain no dissolved salts or minerals. Pure water will react with zinc hydroxide quickly to create white rust.
Acid or acid rain, will accelerate the deterioration of the zinc finish.
Passivators are a coating applied at time of manufacture to protect the zinc. 14

15. Causes Of Paint Film Failures (New )
Faulty Products %
Unforeseen Circumstance 10-15%
Improper Specification 25-30%
Improper Prep/Application 45-55% 15

16. THERE ARE TWO (2) MAJOR CAUSES
FOR IMPROPER
COATING SPECIFICATIONS 16

17. 1. Inadequate or incomplete project information
2. Lack of product knowledge 17

18. PROJECT INFORMATION NEEDED…….18

19. EXISTING SURFACE CONDITIONS
CUSTOMER
NEEDS
DETERMINE
COATING
SYSTEM
EVALUATE
THE
ENVIRONMENT
DETERMINE
SURFACE
PREPARATION
EVALUATE
SERVICE
REQUIREMENTS
EVALUATE
EXISTING SURFACE CONDITIONS 19

20. What are the Goals of Surface Preparation?
To provide a surface suitable for painting by:
Removing contamination
Providing a surface profile
Removing or smoothing irregularities (pits, projections, sharp edges)
Removing tightly bound mill scale & rust 20

21. What Surfaces Require Preparation?
Iron and Steel
Galvanized Metal
Aluminum
Copper
Miscellaneous metals
Pre-Coated Metal Siding
Previously Painted 21

22. CORROSION !
HOW MUCH ? 22

23. 23

24. Results of Pin Hole Rusting of the Primer24

25. What is the Environment?
Type – P
Type – M
Type – C or
Type – A 25

26. Type P: Protected Architectural26

27. Type P: Protected Architectural
Not subject to chemical contaminants
Normal humidity range
Normal industrial interior
Corrosion of steel or galvanized surfaces negligible 27

28. Type M: Moderate 28

29. Type M: Moderate Exterior weathering Normal industrial atmosphere
Moderate concentrations of chemical fumes
Corrosion of steel < 3 mils / year and galvanized substrates negligible
Concentrations of chemical interior – light to moderate fumes without humidity 29

30. Type C: Corrosive 30

31. Type C: Corrosive Moderately aggressive chemical fumes, mists or dust
Corrosion of steel mils / year and galvanized substrates < 1 mil per year
Adjacent to Type A: but at least
30 yards away 31

32. Type A: Aggressively Corrosive32

33. Type A: Aggressively Corrosive
Immersion service
Excessive exposure to aggressive chemical fumes, mists dusts or contaminates
Corrosion of steel > 6 mils / year and galvanized substrates > 1 mil per year
Usually confined to an area within 30 yards from corrosion source 33

34. Application Apply the coating system using one manufacturer
Apply according to the manufacturer’s recommendations
Apply to the Dry Film Thickness (DFT) as stated by the manufacturer
Recoat within the window specified by the manufacturer
The finish system shall be a solid uniform finish free of voids and pinholes. 34

35. Factors Affecting Coating Performance
Design
Coating
Application
Protection
Structural Design (We can’t control)
Coating Selection
Surface Preparation
Surface Prep. 35

36. A Poor Design 36

37. Other Design Considerations
Surfaces should be smooth (e.g. welds)
Welding preferred to riveting
All surfaces should be well drained
Stiffening members should be on the outside surface of tank or vessel 37

38. THANK YOU PROVIDER J476
Corrosion & Premature Coating Failures in Metal 38