What Effect Does Waterjet
Cleaning Have on the Surface?
Thirty Years Perspective
Lydia Frenzel
Advisory Council
San Marcos TX
www.advisorycouncil.org
1
Change introduced by High Pressure
Waterjet Cleaning of coatings
Refresher on the changes over the past 30
years (Water Blasting to Water Jetting)
 What I guessed and predicted in 1976
 We had a great tool-how could we use it
 The development of what we mean by a
“CLEAN SURFACE” today

2
References
JPCL Ebook on Waterjetting
 Blogs by Dr. David A. Summers

– bittooth.blogspot.com (10 years of WJ blog)
– waterjetparts.com/h2o/blog/
David Summers, “Waterjetting Technology”
 Andreas Momber, “Hydroblasting and
Coatings of Steel Structures”
 Paintsquare.com
 Advisorycouncil.org or flashrust.org

3
JPCL Webinars
•
•
•
•
Joao Azevedo, Paint Manufacturer, 2014-11-25
Considerations for UHP WJ
Peter Ault, Specifier, Inspector, 2014-09-02
Performance
Richard Dupuy, Contractor, 2013-05-20,
Operations, Equipment
Richard Burgess, Inspector, 2012-07-09
WaterJet Standards
4
Clean means “Creating the situation
so a coating will perform as expected.”
What kind of surface do we need to
make the paint stick?
What we mean by “clean” has changed over
the past 30 years.
 We used to think that “clean” was to make a
visual appearance with a profile.
 Now we understand that we can “clean” a
surface without changing the profile.

5
Dynamics- Abrasives Compared
to Water
Solids hits from the TOP.
abrades-erodes-erases-moves metal aroundgets embedded- makes hackles
 Changes the profile- Always?
 Water drills into crevices and shears to the
sides.
 Waterjetting can change the character of the
surface while the profile remains the same.

6
John Keane, Surface Profile for Anti-Corrosion Paints
SSPC 74-01, 1976
7
1970’s-1980’s
Abrasive blast
Normal
appearance for
clean steel
8
Top view- abrasive blast
9
Cross view- abrasive blast
Rust-Back
10
Abrasive blast cleaning, multiple passes
Courtesy, Bill Hitzrot, Chesapeake Specialties, 1975
11
Change of profile with overblasting
12
White Metal -Abrasive Blast
Rust Back- White one dayBlack areas- formed overnight
13
Typical abrasive plowing of
surface

Courtesy of High Pressure Waterjet Lab, Missouri Institute
of Science and Technology, Rolla. Dr. David Summers
14
What did we see in 1976-1980
for high pressure waterjetting?
Waterjet cleaned surface looked DIFFERENT
from an abrasive cleaned surface.
 10,000 psi (50-70 MPa) did not deliver
enough energy to surface to disrupt old rust
bond to surface.
 Appearance opposite to abrasive blast.
 Water wetted the entire surface.
 Surface turned blue to golden instantly.
15
20,000 psi
140 MPa
(1983)
Dull gray.
Continue to
see “paint”
stain
16
140 MPa (20,000 psi)- Top view
pattern under corrosion
Sharp and
“clean”
Orginally rounded profile?
17
140 MPa (20,000 psi) Top View
pattern under corrosion.
The “profile” produced at the
beginning affects the future.
Originally
Angular grit
profile
18
140 Mpa (20,000 psi) Side View
Waterjet Cleaning
19
Flue gas scrubber which has
failed
20
Abrasive Cleaning –very slow
Looks good underneath
21
Waterjet (Fan Jet) is about 20 times faster.
Reveals that the entire surface is corroded.
22
Cross section of flue gas
substrate after cleaning.
23
Three basic “terms” of rust found in
standards

Flash Rust is an oxidation of the steel that occurs as wetted carbon
steel dries OR rusting that occurs when a thin coat of waterborne paint is
applied over blast cleaned steel. Often looks like rust bloom.

Rust-Back (rerusting) is rusting that occurs when freshly exposed,
dry, bare steel is exposed to conditions of high humidity, moisture, or a
corrosive atmosphere. It is the term used when steel cleaned by dry abrasive
blasting, power tools, or wet abrasive blasting begins to rust after the steel
surface has completely dried.

Rust Bloom is somewhat uniform rust spread evenly over a large
section of the surface.

Long term corrosion is not flash rusting.
24
You must get the energy to the surface
to disrupt the bond.
10,000 psi
20,000 psi
25
1983, approximately 1/3 meter x 1/3 meter
Manually held fan jet. Appeared to be “instant” conversion
to inert golden color. Stays that way for days.
26
The yellow- golden color is a “Thin Film” refraction.
Courtesy of Union of American Hebrew Congregation
Temple Israel WRJ, Colonial School for the Visually Impaired
27
Light flash rust
USS Boxer, LHD 4 San Diego 2002
Courtesy: Y & T Consulting
28
Typical waterjet response
Now let’s move to re-rusting on steel after
cleaning.
 Grade BC steel – cleaned January 1997 as
part of WJ standards preparation.
 Put over water in 2000.
Photo taken June 2006
 Still looks the same

29
Test- Wet Abrasive Blast
SB 1999-10-16
SB 1999-11-01
SB 1999-10-25
1999-11-11
1999-12-04
30
What happens to corrosion sites?
Take panels from same source
 Blast one with abrasive
 Pressure wash one, followed by abrasive
 Blast one with UHP WJ
 Dry with compressed air
 Put inside over water. Leave alone.
 Observe.

31
Abrasive blast- 6 years

Blasted 2000 to white metal. Placed over water.
Typical original
plate- 2000
May 2006
1.
32
WJ- cleaned in 2000placed over water.
June 2006 WJ
Water dripped on the surfate
left gelatinous rust
Close UP
33
AB steel –cleaned with UHP WJ- June 2006

Stain
stayed
on.
Light
Flash
Rust.
2006-Nov
34
WJ plate re-cleaned June 2006
June 2006
Cleaned with
280 MPa
UHP WJ
After cleaning with
UHP WJ.
2006-Nov
35
Direct impact - side shear forces
Vertical
Velocitypressure
HorizontalShearvolume
36
Water Surface
Diagram - Roland Lever, 1995, NACE Infrastructure- Baltimore
Streamlines change direction due to spinning nozzle
Flexing Action
Impact Induced
Cohesion Erosion
Shear
Loading
Horizontal flow over irregular surface & rapid changes in flow direction
as nozzle spins & moves induces high shear loads at base of any protrusion
and high bending moments.
37
Thick abrasion-resistant nonskid.
Effect of pressure to drill through
coating
38
Removal of coating from cabinet
uses mass-flow-hydraulic shear
39
Focused path of multi-orifice
rotating nozzle

View of flat surface treatment using rotary
head equipped with two water nozzles
P. Borowski, 2005 WJTA Conf., Rotation Water Jet Kinematics; photo-G. Kuljian
40
Wetting characteristics of surface
change significantly
WJ
Degreased
Degreased
McGaulley, W, Shepperson, W., & Berry, Fred, “Comparison of Secondary Surface Preparation
over Water Jetted Surface and Effect on Coatings Performance”, SSPC 2001 Conference
41
Waterjet peening
WJ cleaning
can influence
the energy of
the substrate
surface and
enhance
fatigue
strength.
Kunaporn, WJTA Proceedings 2001, 2003
42
“Erosion of steel substrates when exposed to
Ultra-Pressure waterjet cleaning systems”


Material (steel)
is eroded during
the first two
passes.
Subsequent
passes do not
remove more
material.
DON’T let the
nozzle stop!
.700
1
.009
2
.017
3
.018
Miller & Swenson, WJTA Proceedings, 1999
6
.018
43
Influence of depainting method on substrate
surface profile- WJTA, 2011
Original topography before coating
After paint stripping with grit- overblast
After paint stripping with WJ. Return to original profile
44
Profile. Bronze William Penn Statue
(Boot)- Philadelphia City Hall
Before Cleaning
After Cleaning
Photo courtesy of Rod Draughon- 1989 NACE Corrosion 119
45
Microscopic View
Bronze statute -white corrosion
UHP WJ can be used on “soft” metals.
Photo courtesy of Rod Draughon- 1989 NACE Corrosion 119
46
Lawrence Crum, Univ of Wash, ACS
“Chemistry,” Summer, 2000, p. 20,
Sonochemistry
Cavitation near a solid surface can induce a microjet of
liquid that stream through the bubble upon implosion.
1.
A 100 micron droplet can get into a 10 micron crack.
47
SonoChemistry

www.scs.uiuc.edu/suslick, “The Chemistry of
UltraSound,” by Kenneth S. Suslick

The time of impact is short – so power level
is high.
This is taking place
In some of the areas of
The nozzle stream.
The result- That
“instant” gold ColorIncreases chemical
Reactivity.
48
VanKuiken Patent
5,380,564 (1995)
Aluminum
Grit Blast
 Thermal Spray Coating
Adhesion 3000 psi

Waterjet
 10-75 micron profile
 Thermal Spray Coating
Adhesion 6000 PSI

49
VanKuiken Patent 5,626,674 (1995)
Aluminum
50,000 psi (350 MPa) 1 gallon (3.8 liters) per minute
50
Surface roughening of metallic substrate
by high pressure pure waterjet
350 MPa (50,000 psi) (Steel alloy Threshold
pressure)
“Excellent bonding of a thermal spray overlay was
obtained with this surface preparation having an
absolutely clean interface.”
…the detail of the eroded surface increases with
increasing magnification, suggest the waterjet erosion
produces a fractal surface. … granular features of
about 2 microns … rather micro-faceted.



Surface and Coatings Technology, Vol 76-77, p. 95-100, 1995
51

Profiles in Steel
Abrasive created
WaterJet created
52
What makes a good surface for coatings?
Molecular bonding- mechanical bonding
 Expansion of surface area increase the
number of potentially reactive sites…for
primary or secondary bonding.
 The thin, impermeable oxide layer that
immediately reforms on newly bared iron
surface is .. adherent and suitable as a
substrate for good adhesion.

C. Hare- JPCL 1996 -1999 series
53
– Reassurance –
In order to erode steel in a system
that is set up for cleaning, you would
need approximately 150 times more
energy density than is normally
found in the 280 MPa (40,000 psi)
system.
54
Clean means “Creating the situation
so a coating will perform as expected”

What kind of surface do we need to make
the paint stick?
–
–
–
–

Maximum surface area
Maximum Wetting Properties
Lack of Embedded Material
Removal of non-visible- oil, grease, dirt, salt
Are we looking for longevity or short term
– Asset management
55
Abrasive Cleaning and Pressurized
Water Cleaning are Two Different Tools








Dry or Wet Abrasive
New and Repair
Makes new profile
WaterJet
Repair
Exposes profile
under paint or corrosion
Erases from the Top
Shears at interface
Looks Uniform
Exposes all problems
Cleans top, leave
Gets into crevices,
material in crevices
Could leave top
(stain)
material
NO Rust Back Allowed (Dry)
Flash Rust allowed
Flash Rust Allowed (Wet)
56
What kind of surface do we need to
make the paint stick?
A high ratio of surface area to unit
planar area
Reactive sites over the entire surface
Excellent Wetting Properties
Lack of embedded material
57
Summary






Over the past 30 years, we have changed our concept of
what type of surface we must achieve in order to be
“clean.”
Surface Preparation- Creating the situation so the coating
will perform as expected.
We used to talk about the “process” (abrasive blasting)
for a clean surface.
Now we talk about the end result-performance for a
“clean” surface.
Around 1994- the industry had the “AHA” moment
– It’s waterjetting, not abrasive blasting.
WJ has fundamentally changed our language and concept
of what is occurring at the surface and what we are trying
to achieve.
58
Where to use Waterjetting?
See JPCL, Dec., 2002, p. 57-65
59
Automation
Major chemical manufacturers are
advocating that hand-held waterjetting
cleaning is minimized.
 Equipment will be shown WJTA- IMCA BiAnnual Conference- November 2-4, 2015
New Orleans
 www.wjtaimca2015.com
 YouTube videos and “Basics” slides from
WJTA 2013 are online.

60
Industry Best Practices for
Hydroblast Hose Assembly
Applications
NAHAD Hose Safety Institute
Whitepaper (2014):
 Safety First…the New Normal in High
Pressure Hydroblasting
 Color Coding of Hoses
 http://www.wjta.org/images/wjta/hydroblast
_whitepaper.pdf
61

Slide of inside corner – outside
corner cleaning heads wt vaccuum
62
Under development- reported in March, 2015Fast, smooth coatings removal
63
Hand tools with surfacedetection sensors
64
No trigger pressure, no tumble box,
electronic on-off;
ergonomic design-used in Europe
65
Early Days
66
Cut resistant
clothing is
becoming more
operator friendly
67
Modular Units and Coveralls
68
Eliminate the shredded boot!
69
Any questions??
www.paintsquare.com
Grade D
Optimized removal Parameters
70