Power Washing and Overcoating is Effective and
Much Less Expensive than Sandblasting and
Completely Repainting a Bridge
by
Wayne Senick,
Technical
Director
and
Craig Ballinger,
P.E.
Termarust
Technologies
Abrasive Blasted
High Pressure Water Cleaned
Advantages of Abrasive Blasting
and High Pressure Water Cleaning
Abrasive Blasting
• Removal Of Lead based
paint
• Prepare surface for zinc
based coating
• Cosmetics
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HPWC
Effectively cleans structure
critical crevice corroded
connections
Cost effectively removes
Non Visible contaminants
Provides a stable substrate
for over coating
Potential for at least 50%
project cost savings
These Crevice corroded connections were not washed
before coating to remove the active salts, not chemically
treated to neutralize the active corrosion causing chemistries
and were then sealed - which created an oxygen
concentration cell and failure occurred
1 yr old 3 coat zinc epoxy urethane
over pack rust
Crevice Corroded Connection Washed
before Abrasive Blasting and Coating
• to remove the active salts
• chemically treated with
HR CSA penetrant to
neutralize the active
corrosion causing
chemistries
• sealed up with a top coat
based on HR CSA*
neutralization chemistry
• Coating failure has not
occur in 18 years
*HR CSA (High Ratio Co-Polymerized
Calcium Sulfonate)
Crevice Corroded connections treated with
an HR CSA* corrosion control coating on
the High Level Bridge Edmonton, Alberta,
Canada after 18 years the crevice corrosion
has been stopped
Pack rust and Crevice corrosion can overstress
structural connections
This structure has coating failure in the joints and
connections, caused by severe crevice corrosion and pack
rust, but the coating on the flat surfaces is relatively intact
Typical Recycling Equipment and Negative
Air Containment used in Abrasive Blasting
and Lead Removal Operations
Grit recycling unit and air mover with bag house
Two complete negative air grit recycling systems
with air compressors hooked in a train to be towed
down the bridge as the containment moved
Two example of negative air containments
Water Collection, Containment and Surface
Preparation Equipment for HPWC Lead
Removal Project
Shrink wrapped water tight ultra-light
water collection containment
Movable flow thru tap system to
contain paint chips and liquid water
7000 PSI 6 Gallon per minute hot Water
HPWC Unit with salt remover injector
3-5500 PSI HPWC Units and Injector
for Soluble Salt Remover
Complete Water Recycling and Filtration
System on 100,000 square foot Bridge
Project
Fresh and filtered water storage
Pressure pumps to supply head
pressure of 15 PSI for wash pumps
Settling Tank, Skimmer and Feed
Pumps for Filter System
Water passes thru 5 and 1 micron particle
filters before going to storage for re use
Typical High Pressure Water Cleaning Surface
Preparation Sequence with Adhesion Testing
and Testing for Non–Visible Contaminants
Removal of black oxides by hand or
power tool cleaning
Adhesion Testing using a Hydraulic Pull-off
tester, 300 PSI minimum for over coating, 300
hundred tests per 100,000 sq ft. Photo courtesy
Ministry Transport Ontario
High Pressure Water Cleaning using
5000 PSI, zero degree rotating tip, a 4
inch stand off distance
Testing for Non Visible Contaminants
before coating application
Where are the costs
• Removal of lead based coatings by abrasive blasting and ultra
high pressure water jetting micronizes the lead dust which makes it
breathable and absorbable by plants.
• The containment for abrasive blasting is heavier and more
expensive to construct because of the weight of the abrasive and
the need for negative air pressure to facilitate environmental
protection
• The surface needs to be washed to mitigate salts and the water
must be collected. The washing step must be done, the water must
be removed, and containment dried before blasting can take place
• The equipment required to contain, abrasive blast, collect and
recycle the abrasive is much more expensive to buy and operate
than a high pressure water cleaning system.
Adhesion of Remaining Substrate
• If stressed by HPWC (High Pressure Water Cleaning) at a minimum
5000 PSI with a zero degree rotating tip at a maximum 4 inch stand
off distance specified, adhesion testing in the field has shown that
this surface preparation method consistently will produce adhesion
values over 300 PSI for the remaining coating.
• The owner should specify a minimum adhesion value no less than
300 PSI and adhesion testing must be done before coating is
applied.
• The number of adhesion tests should be written into the
specification. For example: a minimum of 300 tests per 100,000
square feet or whatever the engineer deems necessary based on
the condition of the existing prepared substrate
• Field experience has shown a hydraulic pull off tester meeting
ASTM D4541delivered the most consistent results
Test Site Photos and Adhesion
Test Log Sheets
Site 24, Photo IM000824, 825 PSI
Site 33, Photo IM00833, 450 PSI
Test Site Photos and Adhesion
Test Log Sheets
Site 163, Photo IM001000, 720 PSI
Site 179, Photo IM001022, 340 PSI
Cost Savings Case Histories
Rail Bridge 260,000 square feet
• Total removal of lead
based coating system
• Negative air containment
• Collection, recycling or
disposal of abrasive
• Standard 3 coat zinc
epoxy urethane coating
• Bid price 7.6 million
• No warranty provided
• High pressure water
cleaning and over
coating
• Collecting the lead paint
and recycling the water
• High performance single
coat HR CSA coating
system
• Bid price $4.3 million
• 5 year warranty
including crevice
corroded joints and
connections
Cost Saving including a 5 year warranty = $3.3 million
Contractors Actual Cost Savings
Analysis as Proposed to Owner
Abrasive Blasting - 3 Coat Zinc System vs High Pressure Water Cleaning HR CSA Coating System
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Specified
Air and dust impenetrable enclosure
Alternative
Flow through tarps will trap paint chips and liquid water
Cost saving
Specified
Mechanical ventilation system to protect workers sufficient to achieve a negative air environment within the
enclosure
Alternative
Not required – no lead dust generated
Cost saving
Specified
Exhaust ventilation system to provide filtration of the exhaust air
Alternative
Not required – no lead dust generated
Cost saving
Specified
Weekly instrument testing to verify airflow and negative pressure inside containment
Alternative
Not required – no pressurized containment
Cost saving
Specified
Air lock entry wall
Alternative
Not required – no lead dust to contain
Cost saving
Cost Savings “Continued”
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Specified
Cleaning and securing of containment at the end of workday
Alternative
Not required – no lead dust to blow around
Cost saving
Specified
Daily assessment of visual emissions
Alternative
Not required - no lead dust generated
Cost saving
Specified
Full time or part time high volume ambient air monitoring
Alternative
Not required – no lead dust generated
Cost saving
Specified
Packaging, storage, transportation, and disposal of waste generated by the project
Alternative
Reduction of generated solid waste, approximately 1300 tons.
in addition, no waste solvent, paint cans or catalyzed paint to dispose of
Cost saving
Cost Savings “Continued”
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Specified – coating system
Stripe coat
zinc
1st layer
zinc
2nd layer
epoxy
3rd layer
2k urethane
Alternative
Penetration for joints and connections
Caulk coat + spot prime
Plus 1 layer wet on wet, instead of three
Separate coats with curing time
Cost saving
Specified
Caulking
Alternative
Sealing of joints included in coating operation
Cost saving
Specified – surface preparation
SSPC-SP10 near white blasting and
SSPC-SP7 brush-off blasting
Alternative
Not required
Cost saving
Specified
Measure the surface profile of blast cleaned surfaces
Alternative
Not required – coating not profile sensitive
Cost saving
Cost Savings “Continued”
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Specified
Specified time restriction between cleaning and painting
Alternative
Not required – flash rust not an issue
Cost saving
Specified
Containment during coating application
Alternative
Containment not required for purpose of environmental protection or for a safe working environment.
As coating is not hazardous, will contain overspray with flow through tarps. Cost saving
Specified – recoat time
Apply each coat after previous coat has been allowed to dry
Alternative
All successive coats can be applied wet on wet
Cost saving
Specified – caulking
Caulking shall be applied to crevices not sealed, after the application of the second intermediate layer.
Manufacturer’s note – Caulking must be allowed to cure for 5 – 8 days at 23ºC and 50% R.H.
Alternative
Caulk not required
Cost saving
Specified
Warranty 2 years or 5 years – separate price
Alternative
5 year warranty included
Cost saving
Time Value of Money
Based on a cost saving of $3,000,000.00
Interest Rates
3.5%
5.0%
7.5%
10.0%
Year 1
$3,105,000.00 $3,150,000.00 $3,225,000.00
$3,300,000.00
Year 2
$3,213,675.00 $3,307,500.00 $3,466,875.00
$3,630,000.00
Year 3
$3,326,153.63 $3,472,875.00 $3,726,890.63
$3,993,000.00
Year 4
$3,442,569.00 $3,646,518.75 $4,006,407.42
$4,392,300.00
Year 5
$3,563,058.92 $3,828,844.69 $4,306,887.98
$4,831,530.00
Interest at end of warranty
peroid
$563,059.00
$828,845.00 $1,306,888.00 $1,831,530.00
$1,831,530.00
Time Value of Money
Example of one Owner’s use of the cost
savings from HPWC are as follows:
• Cost saving will be invested during the 5 year
warranty period ( shown on chart )
• On going maintenance program will be
funded with earned interest
• After the 5 year warranty period the saved
capital can now be used to fund another project
Case History Highway Bridge
100,000 square feet
• Total removal of lead
based system
• Negative air containment
• Collection, recycling or
disposal of abrasive
• Standard 3 coat zinc
epoxy urethane coating
• Bid price 3.5 million
• No coating system
performance warranty
available
• High pressure water
cleaning and over
coating
• Collecting the lead and
recycling the water
• High performance
single coat HR CSA
coating system
• Bid price 1.2 million
• 5 year warranty
including crevice
corroded joints and
connections
Cost Saving including a 5 year warranty 2.3 million dollars
Example Specification
Surface Preparation
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SURFACE PREPARATION AND CLEANING:
High Pressure Water Cleaning - The structure (or the portions of it to be coated) are to be cleaned using a 7,000
psi 6 Gal/Min hot water HP WC (high-pressure water cleaning)– with a zero degree rotating tip (at a maximum of a
4” standoff distance) to a (SSPC –SP12 WJ4- NV2 ) to remove loose paint and loose rust (SSPC SP2 &SP3 hand
or power tool cleaning maybe used in inaccessible areas or when water cleaning is not possible). In some cases
after HP WC there are areas of tightly adhered black oxide which was not removed. This tightly adhered black
oxide even though it meets the WJ4 standard (and the active corrosion under it) is highly contaminated with
Chloride &/or Sulfates &/or Nitrates and if allowed to remain, will result in delamination of the black oxide substrate
and the coating which has adhered to it and must be removed.
Crevice Corroded Joints and Connections
When using a 7,000 psi 6 Gal/Min hot water HPWC (high-pressure water cleaning) with a zero degree rotating tip
(at a maximum of a “4” standoff distance) to a (SSPC –SP12 WJ4- NV2) The jet must be focused right on the
crevice corroded joints and connections to flush them thoroughly. In addition to properly clean the joints and
connections a soluble salt remover must be incorporated into the wash water. A minimum 100:1 solution of
Chlor*Rid (manufactured by CHLOR*RID International. www.chlor-rid.com 1-800-442-3217 (USA) or 1-888-2795497 (CDN) or equivalent is required to remove as much salt from the joint as possible. This is mandatory when
preparing crevice corroded joints and connections for treatment with the HR CSA Penetrant/Sealer and HR CSA
Primer/Topcoat System.
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NV (Non Visible Contaminants) When it is expected (and/or confirmed by testing) that the surface of the steel is
contaminated with soluble salts (Chlorides &/or Sulfates &/or Nitrates) – the HP WC (high pressure water
cleaning) should be finished with or incorporated into the wash water initially a 100:1 solution of Chlor*Rid
(manufactured by CHLOR*RID International. www.chlor-rid.com 1-800-442-3217 (USA) or 1-888-279-5497 (CDN)
or equivalent to remove those salts. (Just washing with water is not adequate because the salts are chemically &
polar attracted to steel) [For additional information on this topic please access chlor-rid’s website]
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DRYING: It is required that even if the joints and connections look dry - that they be blown dry with
clean, DRY, oil free, high pressure ( 100 psi) compressed air.
Example Specification
Key Points
• Testing to determine whether or not wash water
is hazardous
• If water is hazardous - establish a collection and
recycling or disposal system
• Collection of any hazardous material including
paint chips
• Do adhesion test to verify surface preparation
has been done correctly
• Do testing to determine non visible contaminants
have been removed to acceptable levels
Conclusion
• High Pressure Water Cleaning and a HR CSA coating
system is a cost effective alternative to Abrasive
Blasting especially on structures with structure
critical crevice corroded and pack rusted joints and
connections
• In most cases washing is now specified for all painting
projects for removal of non-visible contaminants
• The condition of the existing coating is not an issue as
the HPWC surface preparation will remove any coating
not suitable for over coating as proven by adhesion
testing done in the field
• The cost saving can be used to fund other projects
or invested to fund the long term maintenance of the
structure especially for private owners and toll
authorities.