Chapter 7 Pre-Cleaning Flashcards
- Which of the following are visible contaminants?
(Select all that apply)
A. Dust
B. Grease
C. Dirt
D. Oil
E. Salts
✅ A. Dust
✅ B. Grease
✅ C. Dirt
✅ D. Oil
Explanation:
Visible contaminants are those that can be seen with the naked eye.
Dust, grease, dirt, and oil are all readily observable on a surface and can interfere with coating adhesion.
Salts (E) are not visible under normal conditions; they require chemical testing (e.g., Bresle test or salt contamination test) to detect.
Why is this important?
These contaminants must be removed before surface preparation and coating application to prevent adhesion failure, defects, and premature coating breakdown.
SSPC-SP 1 (Solvent Cleaning) is typically used to remove oil, grease, and other organic contaminants before further surface prep.
SSPC-SP 1 is a standard that focuses on which of the following?
(Select all that apply)
A. Removal of nonvisible contaminants
B. Removal of visible and nonvisible contaminants
C. Removal of visible contaminants
D. Solvent Cleaning
E. Mill Scale
✅ B. Removal of visible and nonvisible contaminants
✅ C. Removal of visible contaminants
✅ D. Solvent Cleaning
Explanation:
SSPC-SP 1 (Solvent Cleaning) is the first step in surface preparation and is used to remove visible and nonvisible contaminants such as oil, grease, dirt, and other organic residues before further preparation.
Solvent cleaning is typically performed using methods such as wiping, immersion, vapor degreasing, or pressure washing with approved solvents or detergents.
A (Removal of nonvisible contaminants only) is incorrect because SSPC-SP 1 also removes visible contaminants.
E (Mill Scale) is incorrect because SSPC-SP 1 does not remove mill scale; abrasive blasting or power tool cleaning is required for that.
Why is SSPC-SP 1 important?
Ensures the surface is free from contaminants that could interfere with adhesion.
It is a preliminary cleaning step before other surface preparation methods such as abrasive blasting (SSPC-SP 10) or power tool cleaning (SSPC-SP 3, SSPC-SP 11).
Which of the following methods can remove soluble salts?
(Select all that apply)
A. Solvent Cleaning
B. Pressure Washing
C. Waterjetting
D. Abrasive Blasting
✅ B. Pressure Washing
✅ C. Waterjetting
Explanation:
Soluble salts (e.g., chlorides, sulfates, nitrates) are contaminants that can cause osmotic blistering and premature coating failure if not removed before coating application.
B. Pressure Washing – High-pressure water (with or without cleaning agents) effectively removes soluble salts from the surface.
C. Waterjetting – Ultra-high-pressure waterjetting (UHP) is the most effective method for removing soluble salts, rust, and old coatings.
Why not the other options?
A. Solvent Cleaning → Does not remove soluble salts; it is effective for oil, grease, and organic contaminants but not water-soluble contaminants.
D. Abrasive Blasting → Ineffective for soluble salts because it removes coatings and rust but does not dissolve or wash away salts embedded in the surface.
Best Practices:
Soluble salt testing (e.g., Bresle Patch Test) should be performed before coating.
After pressure washing or waterjetting, surfaces should be dried and rechecked to ensure salts are fully removed.
At what stages of a coating project could pre-cleaning the surface be required?
(Select all that apply)
A. Before the surface preparation (i.e., abrasive blasting, power tool cleaning)
B. After surface preparation, but before the start of coating application
C. In-between the application of each coating material (i.e., primer, intermediate coat, topcoat)
D. Before the dust and dirt has been brushed or wiped from the surface
✅ A. Before the surface preparation (i.e., abrasive blasting, power tool cleaning)
✅ B. After surface preparation, but before the start of coating application
✅ C. In-between the application of each coating material (i.e., primer, intermediate coat, topcoat)
Explanation:
Before surface preparation (A)
Pre-cleaning removes oil, grease, and other contaminants that could cause surface preparation methods (e.g., abrasive blasting) to embed contaminants into the substrate.
SSPC-SP 1 (Solvent Cleaning) is often performed at this stage.
After surface preparation, but before coating (B)
Ensures the removal of residual blasting media, dust, and loose contaminants that could affect coating adhesion.
Compressed air, vacuuming, or solvent wiping is used to achieve proper cleanliness.
In-between coating applications (C)
Prevents contamination from dust, debris, or overspray between coats.
Ensures proper adhesion between primer, intermediate, and topcoat layers.
Why not (D)?
❌ D. Before the dust and dirt has been brushed or wiped from the surface
The wording suggests pre-cleaning before removing dust and dirt, which is not logical because brushing/wiping is part of the cleaning process itself.
Conclusion:
Pre-cleaning is critical at multiple stages of a coating project to ensure adhesion, prevent contamination, and achieve the best coating performance and longevity.
Four (4) Typical SSPC-SP 1 pre-cleaning methods include:
✅ 1. Solvent Wiping
Using rags, wipes, or lint-free cloths soaked in an approved solvent to remove oil, grease, and other contaminants.
Common solvents: Acetone, MEK (Methyl Ethyl Ketone), xylene, isopropyl alcohol.
✅ 2. Vapor Degreasing
Uses heated solvents to create vapors that dissolve and remove contaminants.
Commonly used in industrial applications for parts cleaning.
✅ 3. Immersion Cleaning
Submerging parts or surfaces into a tank of solvent or cleaning solution to dissolve contaminants.
Effective for small parts and equipment.
✅ 4. Pressure Washing (with Detergents or Solvents)
Uses high-pressure water spray (with or without cleaning agents) to remove contaminants.
Effective for large surfaces, removing soluble salts, grease, and dirt.
Why is SSPC-SP 1 Pre-Cleaning Important?
Prevents contaminants from being embedded into the substrate during abrasive blasting.
Ensures proper adhesion of coatings.
Required before any other surface preparation method (e.g., SSPC-SP 10, SSPC-SP 6).
Which of the following cannot be removed by solvent cleaning? (Select all that apply)
A. Mill scale
B. Organic materials
C. Inorganic materials
D. Fingerprints
✅ A. Mill scale
✅ C. Inorganic materials
Explanation:
Solvent cleaning (SSPC-SP 1) is used to remove organic contaminants like oil, grease, and fingerprints.
A. Mill scale → Cannot be removed by solvent cleaning; it requires abrasive blasting (SSPC-SP 10), power tool cleaning (SSPC-SP 11), or pickling.
C. Inorganic materials → Solvent cleaning is not effective for removing rust, oxides, or salts, which require mechanical or chemical cleaning methods.
Why not the other options?
B. Organic materials → Can be removed by solvent cleaning because it dissolves oils, greases, and resins.
D. Fingerprints → Can be removed by solvent cleaning because they contain oils and organic residues.
Conclusion:
For mill scale and inorganic contaminants, you need abrasive blasting, power tool cleaning, or acid pickling, not solvent cleaning.
13.3 Salt Contamination
The inspector shall test for salt contamination if any freshly blasted steel shows patches of
discoloration of black or brown rust within an hour of blasting. To test for contamination:
Total dissolved salt contamination shall be determined as per ISO 8502-6 & ISO 8502-9 bresle
patch and conductivity meter.
A minimum of one residual test shall be conducted per work lot.
If contamination exceeds the specified limit, cleaning using a freshwater rinse and then re-blasting
to the specified cleanliness standard shall be repeated.
The average residual chloride contamination on any bare metal shall be less than 50 milligrams
per square meter (5 μg/cm2) with no single reading above (7μg/cm2).
A. When is soluble salt testing required?
B. What method(s) should be used to test for soluble salts?
C. What concentration of soluble salts is permissible?
D. What steps should be taken if the permissible amount is exceeded?
A. When is soluble salt testing required?
✅ Soluble salt testing is required if freshly blasted steel shows patches of discoloration of black or brown rust within an hour of blasting.
This indicates possible soluble salt contamination, which can cause osmotic blistering and coating failure.
B. What method(s) should be used to test for soluble salts?
✅ ISO 8502-6 & ISO 8502-9 Bresle patch test and conductivity meter
The Bresle patch method extracts soluble salts from the surface and measures their concentration using a conductivity meter.
These methods are industry standards for detecting chlorides, sulfates, and nitrates, which are harmful to coating adhesion.
C. What concentration of soluble salts is permissible?
✅ The average residual chloride contamination should be less than 50 mg/m² (5 μg/cm²), with no single reading above 7 μg/cm².
This limit helps prevent osmotic blistering and ensures the coating system performs properly.
D. What steps should be taken if the permissible amount is exceeded?
✅ If contamination exceeds the specified limit:
Freshwater rinse – Use high-pressure fresh water to remove the salts.
Re-blasting – Once dry, re-blast the surface to the specified cleanliness standard.
Retesting – Conduct another soluble salt test to confirm contamination is below permissible levels before applying the coating.
Conclusion:
Soluble salt testing is critical for ensuring coating adhesion and preventing premature failure. If salt contamination is detected, the surface must be cleaned and re-blasted before proceeding with coating application.
