2. SCOPE
• Introduction
• Importance of Surface Preparation
• Surface Preparation Standards
• Industrially Adopted Surface Preparation Methods
• Need for new methods
• Plasma Treatment
• Conclusion and Prospect
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3. INTRODUCTION
• The task of cleaning the surface properly to ensure better performance, service life
and quality of coating.
• Undertaken to remove dust, grease, rust or old coating layers from the surface to be
coated.
• It not only cleans, but introduces a suitable profile to receive the protective coating.
• Most critical pre-coating treatment of any substrate.
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4. INTRODUCTION
• Universally accepted as the most important factor affecting the overall success of a
corrosion protection system.
• A majority of large scale industries have been following age old techniques towards surface
preparation.
• Amidst the constant corrosion protection requirements and the finances involved in doing
so, the deteriorating impacts of these techniques are often ignored.
• With increased awareness, there arises a need to study and adapt new techniques on
industrial scale.
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5. IMPORTANCE OF SURFACE
PREPARATION
• To promote coating adhesion to the substrate.
• Improve durability of coating.
• Better strength and appearance.
• To save time and money.
• Reduce failures and costly re-works.
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6. SURFACE PREPARATION STANDARDS
• Specified by Society for Protective Coatings (SSPC), National Association of
Corrosion Engineers (NACE) and British Standards European Norms (BS EN).
• Surface preparation accounts for about 40 % of the cost of the repainting project.
• Standards exist to maximize coating life and minimize costs.
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7. SURFACE PREPARATION STANDARDS
• SP 1 / ISO 8504 (Solvent Cleaning)
• Washing with soap, water and rag.
Acceptable limit
• Loosely adhering material :
• Tightly adhering material :
• Stains, steaks and shadows
100 %
100 %
: 100 %
• Cleans the surface of contaminants smeared over the surface.
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8. SURFACE PREPARATION STANDARDS
• SP 7 /NACE # 4 / SA 1 (Brush-Off)
• Light Blast cleaning, sweep blasting.
Acceptable limit
• Loosely adhering material :
• Tightly adhering material :
• Stains, steaks and shadows
0 %
100 %
: 100 %
• Removes loose rust, mill scales, coatings and uniformly roughens the surface.
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9. SURFACE PREPARATION STANDARDS
• SP 14 /NACE # 8 (Industrial Blast Cleaning)
• Most recent abrasive blasting standard.
Acceptable limit
• Loosely adhering material :
• Tightly adhering material :
• Stains, steaks and shadows
0 %
10 %
: 100 %
• Preferred when existing coating is thin, well adherent and compatible with new
coating.
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10. SURFACE PREPARATION STANDARDS
• SP 6 /NACE # 3 /SA 2 (Commercial Blast Cleaning)
• Thorough blast cleaning.
Acceptable limit
• Loosely adhering material :
• Tightly adhering material 0 %
• Stains, steaks and shadows :
0 %
:
33 %
• Preferred when high, but not perfect cleanliness warranted.
• Products serving in non-corrosive environment.
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11. SURFACE PREPARATION STANDARDS
• SP 10 /NACE # 2 /SA 2.5 (Near White Blast Cleaning)
• Very thorough blast cleaning.
Acceptable limit
• Loosely adhering material :
• Tightly adhering material :
• Stains, steaks and shadows
0 %
0 %
: 10.5 %
• Required for high performance coatings over steel exposed to severe environmental
conditions.
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12. SURFACE PREPARATION STANDARDS
• SP 5 /NACE # 1 /SA 3 (White Metal Blast Cleaning)
• Blast clean to visibly clean steel.
Acceptable limit
• Loosely adhering material :
• Tightly adhering material 0 %
• Stains, steaks and shadows :
0 %
:
0 %
• Required for steel exposed to high temperature, high pressure and corrosive environment.
• Used where coating failures can result in catastrophic failures.
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13. INDUSTRIALLY ADOPTED SURFACE
PREPARATION METHODS
• Methods that have been tested, modified and adopted to suit the ever increasing
industrial requirements.
• Sand Blasting
• Water Blasting
• Hand & Power Tool Cleaning
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14. SAND BLASTING
• Most adopted surface preparation method worldwide.
• Employs High pressure air combined with abrasive for cleaning.
• Easier and faster compared to other methods.
• Variation in pressure can create profile varying from SA3 to SA1.
• Used in shipbuilding industry, bridge paintings etc.
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16. WATER BLASTING
• Safe, eco friendly, economical and efficient.
• Also known as high pressure water cleaning or hydrojet blasting.
• Fan nozzles of various sizes used to adjust pressure.
• Can be used on metals, concrete, plastic, composites etc.
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18. HAND AND POWER TOOLING
• Surface cleaning using hand tools (scrappers, wire brush etc.)
• Useful where abrasive blasting cannot be employed.
• Relatively slower than other methods.
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19. REQUIREMENT OF NEW
TECHNIQUES
• High levels of dust and noise.
• Abrasive material might contain toxic substances.
• Hazardous to operators.
• Silica sand causes lung cancer.
• Harmful to the environment.
• Water injection can be fatal.
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20. PLASMA TREATMENT
• Plasma is generated by supplying energy to gas.
• The energy required can be produced by thermal reaction, applying electric field, magnetic
field of even by nuclear reaction.
• Three significant reactions observed are excitation, ionization and dissociation.
• Concentrated discharge thus generated is used to bombard the substrate at high velocity.
• This cleans, etches and functionalizes the substrate.
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22. DOUBLE GLOW PLASMA SURFACE
TREATMENT
• Although conceptualized in 1980, the process is only recently adopted on industrial
scale.
• Uses double glow discharge phenomenon and low temperature plasma to form
alloy layer with special physical and chemical properties.
• Utilizes ion bombardment, sputtering, space transmission, deposition and diffusion
in low vacuum.
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24. ADVANTAGES
• Can be used on any element of the periodic table.
• Improved surface hardness, wear and corrosion resistance.
• Makes the surface hydrophilic to facilitate coating application.
• Eliminates a majority of hazards associated with previously discussed techniques.
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25. CONCLUSION AND PROSPECT
• Ni-Cr alloy layer formed on carbon steel plate can be used to replace conventional
stainless steel.
• Very high bond strengths can be achieved by forming a metallurgical bond between
the coating and substrate.
• Surface properties of mechanical parts can be enhanced.
• The entire process includes vacuum, glow discharge, ion bombardment, sputtering,
deposition, diffusion, etc. There is no pollution.
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26. CONCLUSION AND PROSPECT
• Low grade materials can be transformed into high quality metals at very low costs.
• The stability of glow discharge and the suppression of arc discharge need to be
further optimized.
• Re-works/ repairs of coatings in use needs to be examined.
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27. REFERENCES
• “A Modern Day Alchemy : Double Glow Plasma Surface Metallurgy
Technology”, Zhong Xu, Research Institute of Surface Engineering,
Taiyuan University of Technology, 2021.
• “Understanding Surface Preparation Standards”,
https://www.graco.com/gb/en/contractor/solutions/articles/surface-
prep-standards- explained-sspc-nace-iso-8501.html
• “What is Surface Preparation (An in-depth guide)”,
https://www.twi-global.com/technical-knowledge/faqs/what-is-surface-
preparation
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