Protective Coating L6- Surface preparation & Paint application - - PowerPoint PPT Presentation
Protective Coating L6- Surface preparation & Paint application MM650/2 Prof. A.S. Khanna Corrosion Science & Eng. IIT Bombay & Prof Siva Bohm Honorary visiting scientist - IIT Bombay Principal scientist - Tata Steel Ltd
Corrosion Science & Eng. IIT Bombay & Prof Siva Bohm Honorary visiting scientist - IIT Bombay Principal scientist - Tata Steel Ltd
High Build Paints & Metal Coatings Thin Film Paints
Shot Grit
– Removal of Contaminants – Standard of Cleanliness – Profile and Amplitude – Additional Treatments – Pre-Coating Condition
– Materials, Application and Finished Job
Pictorial Reference BS 7079: Part A1 / ISO 8501-1
Light
Thorough
Very Thorough
Visually Clean
Thorough
Very Thorough
Manual Compressed Air System
Automatic Wheelabrator System
Modern Automatic Blast Cleaning Plant
Method Effectivene ss (%) Use Manual 25 Maintenance Mechanical 30 Maintenance Flame Clean 35 Maintenance /New Work Dry Abrasive Blast Clean 100 Maintenance /New Work Wet Abrasive Blast Clean 100 Maintenance /New Work Acid Pickling 100 New Work High Pressure Water Jet 100 Maintenance /New Work
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– HVLP – Airless – Air Assisted – Electrostatic
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1. Very Slow Application 2. No Consistancy with film thickness ( Non Uniform coating thickness ) 3. High Fatigue to the applicator 4. Speeds of painting is generally defined by the applicator 5. Applicator is in contact with harmful solvents for longer periods of time. 6. Not suitable for High solids and low pot life paints.
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Advantages
1.
3-4 times faster than Brush
2.
Suitable for Low viscosities
3.
Best suited for low / medium volumes
4.
Superior over Brush finish
5.
Least Expensive
Disadvantages
1.
Slow Application
2.
High Fatigue to the applicator
3.
Speeds of painting is generally defined by the applicators skill.
4.
Applicator is in contact with harmful solvents for longer periods of time.
5.
Not suitable for High solids and low pot life paints.
6.
Cannot be used on all profiles
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A Ad dv va an nt ta ag ge es s L Li im mi it ta at ti io
ns s F Fi in ne e f fi in ni is sh h q qu ua al li it ty y. . E Ea as sy y t to
ve er r-
at to
mi iz ze e a an nd d c ca au us se e e ex xc ce es ss si iv ve e
ve er rs sp pr ra ay y. . F Fl le ex xi ib bl le e
pe er ra at to
r c co
nt tr ro
l
f a al ll l a as sp pe ec ct ts s
f a at to
mi iz za at ti io
n i in nc cl lu ud di in ng g p pr re es ss su ur re e, , f fa an n w wi id dt th h, , a an nd d f fl lu ui id d d de el li iv ve er ry y. . T Ty yp pi ic ca al ll ly y, , t to
mu uc ch h c co
nt tr ro
l f fo
r i in ne ex xp pe er ri ie en nc ce ed d
pe er ra at to
r. . T Ta ak ke es s a an n e ex xp pe er ri ie en nc ce ed d
pe er ra at to
r t to
se et t-
up p t th he e g gu un n f fo
r
pt ti im mu um m p pe er rf fo
rm ma an nc ce e I In ne ex xp pe en ns si iv ve e e eq qu ui ip pm me en nt t r re eq qu ui ir re ed d P Pu ur rc ch ha as se ed d d du ue e t to
pr ri ic ce e t to
ma an ny y t ti im me es s. . E Ea as sy y t to
us se e. . S Si im mp pl le e
pe er ra at ti io
n e ea as sy y t to
pe er ra at te e
ut ts si id de e
f t th he e g gu un ns s d de es si ig gn n l li im mi it ts s. . L Lo
w p pr re es ss su ur re e s sa af fe et ty y. . N No
t r re ec co
mm me en nd de ed d f fo
r p pr ro
te ec ct ti iv ve e c co
at ti in ng g a ap pp pl li ic ca at ti io
n, , T Ty yp pi ic ca al ll ly y t th ho
ug gh ht t
f a as s t th he e
nl ly y w wa ay y t to
ge et t a a g go
d f fi in ni is sh h. . T Tr ra an ns sf fe er r e ef ff fi ic ci ie en nc cy y i is s p po
r, , c ca an nn no
t h ha an nd dl le e h hi ig gh h s so
li id ds s p pa ai in nt ts s. .
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system
feed system
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Air Pressure 20-60 psi 1.5-3.5 bar
Transfer efficiency = 20 - 30%
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Fluid Pressure 5-10 psi .33-.66 bar 1-6 in 25-150 mm
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2000+ psi fluid pressure Transfer efficiency = 50 - 60%
Click to see spray
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by hydraulic force pushing material through an orifice.
between the fluid stream and atmosphere disrupts the stream into small particles.
heaviest spray finish and is measured in gallons per minutes.
priority.
complete pattern .
2000 psi 133 Bar 13.3 MPa Fluid pressure Transfer efficiency = 40-50%
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80:1 33:1 Zinc 24:1 80:1 AA 41:1
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determines the fluid flow and size of the spray pattern
material you will be spraying.
Coating
Material Tip Size ( in.) Stain or Lacquer .011 to .013 Oil Base Paint .013 to .015 Latex Paints .015 to .019 Heavy Latex & Smooth Electrometric .021 to .025 Electrometric and Block Fillers .025 to .035+
Watch for runs or sags in the pattern as a sign of a worn tip. DO not increase pressure of the pump to combat this problem
Simply replace the tip.
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“tails” “tails”
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to airless
to lower fluid flow rates and pressure
reduced particle velocity
the better the finish quality.
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paint sprayed)
Wp = Weight of wet coating on the part Ws = Weight of liquid coating sprayed
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Application Method (Transfer Efficiency) Liters of Paint/Yr Tons of VOC's/Yr Liters of Paint Wasted/Yr Tons of Paint Sludge/Yr Air Spray (30% Efficiency) 5000 7.5 3500 12.25 HVLP (45% Efficiency) 3333 5 1833.3 6.4 Airless ( 50-55%) 2800 3.25 1500 4.5 Air Assisted Airless (60% Efficiency) 2500 3.75 1000 3.5 Electrostatic Air Spray (75% Efficiency) 2000 3 500 1.75 Electrostatic Air Assisted Airless (85% Efficiency) 1765 2.65 265 0.93
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“A” Component Resin Base Prepolymer Polyol Lacquer
“B” Component Isocyanate Catalyst Accelerator Promoter Activator Hardener
( Spray )
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Time
Solid Liquid Working Pot Life Pot Life
Viscosity
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not that critical
mixing quality issues
solvent
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Proportioning
Mixing (Batch Mixing)
Proportioning Systems
Ratio Assurance Devices
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material on demand
Proportioner
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Proximity Sensor Fluid Manifold Integrator
Flame Arc HVOF Plasma
ROTATING BRUSH METERING - DISPERSION VERY HIGH EFFICIENCY CORONA CHARGING
Photomicrographs
Developer particles in the EMB Process
TRANSFER DRUM / BELT
FRICTIONAL (TRIBO) CHARGING
Powder coating applied onto transfer drum and partially covered substrate drum
Partially covered substrate drum