1. Applying Coatings over Flash Rust in a Marine Environment

2. Learning Outcomes
This webinar will discuss the levels of flash rust as defined in SSPC-SP 12, how to evaluate flash rust and the impact it can have on coating performance.

3. Definitions Flash rust Rust-back Rust bloom
Occurs on carbon steel from the time the waterjetting process cleans the surface to the time the water used for the cleaning process dries.
Rust-back
Used in dry abrasive blast standards
Occurs when dry, bare steel is exposed to conditions of high humidity, moisture, or a corrosive atmosphere.
Rust bloom
Generic term to describe uniform rust spread evenly over a large section of a surface

4. Ultra High Pressure Waterjetting
Method of surface preparation
May leave wet surface which can develop flash rust
Two types of equipment
Robotic Method
Closed Loop
Open Loop
Hand Lance Method

5. Robotic Equipment Incorporates water removal devices
Little to no flash rust

6. Hand Lance Equipment Used to clean areas with complex shapes
Do not incorporate water removal devices
Surface tend to remain wet longer and develop flash rust
Can blow down with air to minimize flash rust
Flash rust may require remediation prior to painting
Wiping
Pressure washing
Abrasive blasting

7. Non-Visible Contaminants
SSPC-SP 12 Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating
Visible Contaminants
Non-Visible Contaminants
Flash Rust

8. SSPC-SP 12 Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating
Four levels of visible contaminants
WJ-1 (Clean to Bare Substrate), WJ-2 (Substantial Cleaning), WJ-3 (Thorough Cleaning), WJ-4 (Light Cleaning)
Four levels of flash rust
None, Light (L), Moderate (M), Heavy (H)
Three levels of non-visible contaminants
NV-1 (below detection limits), NV-2 (varying requirements), NV-3 (less than 50 µg/cm² of chloride or sulfate)

9. Coating Over Flash Rust
Requirement depends on coating material, performance expectations, service environment, etc.
Some products and owners allow coatings to be applied over “Moderate” levels of flash rust
Other products and owners only allow coating over “Light” levels or no flash rust

10. Inspecting Flash Rusted Surfaces

11. Flash Rust – How do we describe this?
SSPC-SP 12 Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating
Flash Rust – How do we describe this?

12. SSPC-SP 12 The levels of flash rust are defined as: No flash rust
Light (L)
Exhibits small quantities of a yellow-brown rust layer that is tightly adherent and not easily removed by lightly wiping with a cloth.
Moderate (M)
Exhibits small quantities of a yellow-brown rust layer that is tightly adherent and leaves light marks on a cloth that is lightly wiped over the surface.
Heavy (H)
Exhibits a layer of heavy red-brown rust that hides the initial surface condition completely and is loosely adherent, easily comes off and leaves significant marks on a cloth that is lightly wiped over the surface.

13. Descriptors of Flash Rust- SSPC SP-12/VIS-4
Metric
Light
Moderate
Heavy
Color
Yellow-brown
Red-brown
Substrate
Steel substrate may be observed
Obscures the original steel surface
Hides the initial surface condition completely
“Lightly wiping” with a cloth
Not easily removed
Leaves light marks
Leaves significant marks
Volume
Small quantities of a…rust layer
Exhibits a layer of…rust
Exhibits a layer of heavy…rust
Distribution
Evenly distributed or present in patches
Adhesion
Tightly adherent
Reasonably well adherent
Loosely adherent, easily comes off

14. Descriptors of Flash Rust in SSPC-SP 12/VIS-4
Metric
Light
Moderate
Heavy
Color
Yellow-brown
Red-brown
Substrate
Steel substrate may be observed
Obscures the original steel surface
Hides the initial surface condition completely
“Lightly wiping” with a cloth
Not easily removed
Leaves light marks
Leaves significant marks
Volume
Small quantities of a…rust layer
Exhibits a layer of…rust
Exhibits a layer of heavy…rust
Distribution
Evenly distributed or present in patches
Adhesion
Tightly adherent
Reasonably well adherent
Loosely adherent, easily comes off
What are the differences?

15. Descriptors of Flash Rust in SSPC-SP 12/VIS-4
Metric
Light
Moderate
Heavy
Color
Yellow-brown
Red-brown
Substrate
Steel substrate may be observed
Obscures the original steel surface
Hides the initial surface condition completely
“Lightly wiping” with a cloth
Not easily removed
Leaves light marks
Leaves significant marks
Volume
Small quantities of a…rust layer
Exhibits a layer of…rust
Exhibits a layer of heavy…rust
Distribution
Evenly distributed or present in patches
Adhesion
Tightly adherent
Reasonably well adherent
Loosely adherent, easily comes off
More distinct differences

16. Descriptors of Flash Rust in SSPC-SP 12
Metric
Light
Moderate
Heavy
Color
Yellow-brown
Red-brown
Substrate
Steel substrate may be observed
Obscures the original steel surface
Hides the initial surface condition completely
“Lightly wiping” with a cloth
Not easily removed
Leaves light marks
Leaves significant marks
Volume
Small quantities of a…rust layer
Exhibits a layer of…rust
Exhibits a layer of heavy…rust
Distribution
Evenly distributed or present in patches
Adhesion
Tightly adherent
Reasonably well adherent
Loosely adherent, easily comes off
Not Quantitative
Some distinctions less clear
Which metric takes precedence?

17. How to Determine Level of Flash Rust
NSRP Round Robin data

18. Enhancements/Alternative Tests
Recommended Guidelines for Evaluating Flash Rust (National Shipbuilding Research Program)
“Ten Tape” Test (Hempel)
Tape Transmittance Test (U.S. Navy Adjudication Tool)

19. Recommended Guidelines for Evaluating Flash Rust
Developed by the U.S. National Shipbuilding Research Program
Contains a table which breaks down the flash rust definitions
Discusses impact of inspection conditions
Time, illumination, distance
Provides a more detailed method for performing brush-wipe test
Discusses pressure washing for remediation

20. Suggested “Brush-Cloth” Wiping Test
Recommended to improve consistency of evaluation

21. Suggested “Brush-Cloth” Wiping Test

22. Removal of Flash Rust by Pressure Washing

23. Hempel “Ten Tape” Test
Moderate
Heavy

24. Tape Transmittance Test
Adaptation of Hempel “10 tape” test
Apply tape to flash rust
Rub as hard as necessary with finger
Affix tape to clear glass slide
Measure percent light transmittance through tapes with and without flash rust
Difference between measurements is indicative of flash rust (higher is worst)
Possible Accept/Reject Criteria

26. Works with different tapes and meters

27. “Light” (1-8% Change in Transmittance)

28. “Moderate” (10-20% Change in Transmittance)

29. “Moderate-Heavy” (14-24% Change in Transmittance)

30. “Heavy” (21-50% Change in Transmittance)

31. Applying Coatings Over Flash Rust

32. Concerns Regarding Coating Over Flash Rust
Flash Rust may contain contaminants
Could lead to undercutting, osmotic blistering or loss of adhesion
Surface should be tested for non-visible contaminants
Surface should have been thoroughly cleaned before flash rusting begins
Flash Rust may interfere with adhesion
Does the coating adequately wet the flash rust?
Depends on coating chemistry as well as flash rust

33. Benefit of Allowing Coating Over Flash Rust
Reduce surface preparation cost as more flash rust is allowed
Allows operations to be sequenced more efficiently
One source estimated savings of 20% of typical waterjetting surface preparation cost
Depends on extent of remediation required (e.g., complexity of structure, cleanliness requirement)

34. Suitability of Flash Rust for Coating
Several studies have shown that ultrahigh pressure waterjetting provides an excellent surface for coatings
Most agree that some level of flash rust is acceptable for common marine quality epoxy based coating systems
Typically either “Light” or “Moderate” is the allowable flash rust level
Predominate concern is accurately characterization
Must be cleaned first (i.e., no “old rust”)

35. Laboratory Data
Lab testing suggests Moderate Flash Rust does not significantly impact cathodic disbondment of marine grade epoxies

36. Adhesion Data from Ships In Service

37. Inspecting Coating Over Flash Rust
Validate performance by:
Adhesion Test (Pull-off or knife cut)
Close inspection for corrosion or blistering initiating at difficult to clean surfaces
Chemically removing coating to observe substrate

38. Key Concepts
SSPC SP-12 contains three important criteria for a waterjet cleaned surface
Visible contaminants, Flash Rust & non-visible contaminants
Current flash rust definitions are subjective descriptions of color, appearance and adhesion
Several techniques are available which can improve on the current definitions
Communication between contractor, inspector, owner and coating supplier will facilitate consistent interpretation

39. Key Concepts Flash rust can be painted over successfully
The allowable level depends on factors such as the coating material and service environment
Flash rust can adversely impact coating performance
Can cause poor adhesion or osmotic blistering

40. Thank You For Attending!
Questions?
Thank You For Attending!