Wet abrasive blast cleaning with dust suppression water containing Chlor-Rid was used to prepare the interior surfaces of large tanks for painting, generating much less dust than dry abrasive blasting. The prepared surfaces were found to be free of chlorides and sulfates that could cause coating failure. A low-temperature epoxy coating was applied by a painting contractor and remained in excellent condition with no visible rust after one year of immersion service, demonstrating the success of this innovative painting technique for tanks.

1. EVEN COOLER THAN WATCHING
PAINT DRY!
2010 RISK TAKEN
2011 PROVEN SUCCESS
By John Brodar P.E., SALT RIVER PROJECT

2. In 2010 painting the interior walls
of the Reactivators presented
some problems.
1. Abrasive blast cleaning of the open top tank
would generate a lot of dust.
2. Painting of this tank was not a scheduled
outage task. It was late February when we
decided to paint the tank. Even in March in Page,
AZ it might rain, snow or freeze.

3. It was time for some innovative
painting.
Exciting!

4. Wet abrasive blast cleaning was
used for surface preparation.
The water would control the dust
and eliminate the need and
expense of tenting the 135’
diameter tank.

5. The entire tank wall was blast cleaned to near
white metal with Chlor-Rid in the dust
suppression water.

6. What blast cleaning standard is this surface?
It was abrasive blasted to near white, but with the water ring it was expected to rust. It was not just a water blast cleaned surface
either. Industry standards have not yet caught up to real life applications.
“A Brush-Off Blast Cleaned surface, when viewed without magnification, shall be free of all visible oil, grease,
dirt, loose mill scale, loose rust, and loose paint. Tightly adherent mill scale, rust and paint may remain on
the surface. Mill scale, rust and paint are considered tightly adherent if they cannot be removed by lifting
with a dull putty knife.”
The specification required:
1. A near white level of
initial cleaning,
2. The use of a water ring
for dust control,
3. the use of Chlor-Rid to
decontaminate the steel.
4. The finished surface was
to meet the requirements
for Brush Off Blast
Cleaning, SSPC-SP 7

7. THIS IS A CLOSE UP PHOTO OF THE TIGHTLY ADHERING RUST LEFT AFTER A NEAR WHITE METAL
ABRASIVE BLAST CLEANING. A WATER RING WAS ATTACHED TO THE BLAST NOZZLE FOR DUST
CONTROL. CHLOR-RID WAS ADDED TO THE DUST SUPPRESSION WATER. NOTE THE EVEN LIGHT
BROWN RUST; IT IS INDICATIVE OF A STEEL SURFACE FREE OF NON-VISIBLE CONTAMINANTS. THE
DARKER AREA WAS FROM DISTILLED WATER USED TO TEST FOR CHLORIDES AND SULFATES. THE
BLACK AND WHITE SPOTS ARE REMAINING COAL TAR AND OTHER EPOXY COATINGS.

8. CONTRAST THE EVEN LIGHT BROWN COLOR OF THE PREVIOUS PHOTO WITH THIS ONE. THE DARK
BROWN SITES ARE HEAVILY CONTAMINATED WITH CHLORIDES AND SULFATES.
THE BRIGHT YELLOW POTASIUM FERRICYANIDE TEST PAPER TURNS BLUE WHEN IN CONTACT WITH
DISTILLED WATER APPLIED TO A STEEL SURFACE CONTAMINATED WITH CHLORIDES AND SULFATES.
PAINTING OVER THE CHLORIDES AND SULFATES WILL RESULT IN COATING FAILURE IN 6-36 MONTHS.

9. THE PAINT SELECTED IS A LOW TEMPERATURE VERSION OF THE CARBOLINE
CARBOGAURD 235 SURFACE TOLLERANT EPOXY WE HAVE BEEN USING IN THE
CIRCULATING WATER LINES FOR THE LAST TWO OUTAGES.

10. THE PAINT CONTRACTOR, KEENE COATING, DID AN OUTSTANDING JOB.
THIS IS THE INTERIOR PAINTED SURFACE OF REACTIVATOR 2. IT WAS PAINTED IN 2010
OVER “TIGHTLY ADHERING RUST”. BUT THE STEEL WAS DECONTAMINATED OF
CHLORIDES AND SULFATES WITH CHLOR-RID. THIS AND SUBSEQUENT PHOTOS ARE
FROM 2011, AFTER 1 YEAR OF IMMERSION SERVICE.

11. THE LOWEST FOOT OF THE WALL REVEIVED AN EXTRA COAT OF
PAINT IN 2010. EVEN THE STEEL TO CONCRETE INTERFACE WAS
ENTIRELY FREE OF RUST.

12. THIS 8” NOZZLE HAD BEEN IN SERVCE AND WAS RUSTED PRIOR
TO THE 2010 PAINTING.
AFTER DECONTAMINATION AND PAINTING, EVEN THE THREADS
ARE FREE OF RUST ONE YEAR LATTER.

13. OF THE 10,200 SQUARE FEET OF TANK WALL THAT WAS PAINTED IN 2010,
THIS IS THE ONLY VISIBLE RUST IN 2011 AFTER 1 YEAR OF IMMERSION
SERVICE.

14. REACTIVATIOR 1 IS SCHEDULED TO BE PAINTED USING THE SAME SYSTEM IN MARCH
2011. THE CATHODIC PROTECTION SYSTEMS FOR THESE TWO TANKS WAS
COMPLETELY REBUILT.
WITH NEW WIRE ANODES AND RECTIFIERS, THIS COATING AND THE CATHODIC
PROTECTION SYSTEM SHOULD PROVIDE A MAINTENANCE FREE SERVICE LIFE FOR THE
TANK SHELL AND CENTRAL SUPPORT FOR THE NEXT 20 YEARS.