CLEANING OF CONTAMINATED
GALVANIZED SURFACES
BY TESLA HALL, KURT ETTER, AND THOMAS LANGILL, PHD
BACKGROUND
This report describes numerous cleaning products
that can be used to remove contaminants from the
surface of hot-dip galvanized steel after the parts
have been erected or are in service.
The
contaminants that were used in the tests included
permanent marker, oil, grease, and spray paint. In
parts 1 and 2 of this study, the ability of each
cleaning product to remove the contaminants from
the surface of galvanized steel was tested. Then
in part 3 of the study, the most successful cleaning
products were retested in order to determine
which ones were most effective. The material
safety data sheet (MSDS) for each of the top two
cleaning products was then obtained in order to
look at the environmental, health, and safety
aspects of the product. In Figure 1, a 4” x 8”
galvanized surface that was used for the tests is
shown before any contaminants were applied.
Figure 1: 4” x 8” Galvanized Surface
Before Contaminants Were Applied
TESTS: PART 1
The 4” x 8” hot-dip galvanized surfaces were
divided into four sections that were each covered
with a different contaminant and placed indoors
for 24 hours. The cleaning products were then
applied following the manufacturer’s directions.
The surfaces were then examined to determine
Copyright © 2006 American Galvanizers Association. The material provided herein has been developed to
provide accurate and authoritative information about after-fabrication hot-dip galvanized steel. This material
provides general information only and is not intended as a substitute for competent professional examination and
verification as to suitability and applicability. The information provided herein is not intended as a
representation or warranty on the part of the AGA. Anyone making use of this information assumes all liability
arising from such use.
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Protecting Steel for Generations
how successful each cleaning product was at
removing the contaminants. In Figure 2, one of
the galvanized surfaces that were contaminated
with permanent marker, oil, grease, and spray
paint, from left to right, is shown.
•
•
•
•
Goof Off®
Simple Green®
The Must for Rust®
Stainless Steel Cleaner
TEST RESULTS: PART 1
It was found that the permanent marker, oil, and
grease were easily removed from the hot-dip
galvanized surface using any of the cleaning
products. The spray paint was the most difficult
contaminant to remove.
The two cleaning
products that successfully removed the spray paint
were Comet® and Goof Off®.
Figure 2: Contaminated Hot-Dip Galvanized Surface
1.
2.
3.
4.
5.
6.
7.
PROCEDURE
Take pictures
Cover galvanized panels with
contaminants
Allow to weather for 24 hours
Attempt to clean the galvanized
surface with a single cleaning
product
Rinse surface with water and dry
Evaluate the performance of the
cleaning products
Take pictures
•
•
•
•
CONTAMINANTS
Permanent Marker
Oil
Grease
Spray Paint
•
•
•
•
•
CLEANING PRODUCTS
Vinegar
Ammonia
Comet®
Bleach
Muriatic Acid
Some of the cleaning products removed the
contaminants but changed the look of the
galvanized surface. It was noticed that the
vinegar clouded the appearance of the zinc
coating and possibly removed some of the outer
layer of the coating. When the muriatic acid
solution was applied to the surface, it created a
bubbling reaction everywhere except where the
spray paint had been applied. The ammonia
created a golden appearance on the surface of the
hot-dip galvanized steel. In Figures 3 - 11, the
galvanized plates after cleaning and the name of
the cleaning product that was used on them are
shown.
Figure 3: Vinegar
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Figure 4: Ammonia
Figure 7: Muriatic Acid
Figure 5: Comet®
Figure 8: Goof Off ®
Figure 6: Bleach
Figure 9: Simple Green®
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In Figure 12, one of the galvanized surfaces that
were contaminated with the three different spray
paints is shown.
Figure 10: The Must for Rust®
Figure 12: Contaminated Galvanized Surface
1.
2.
3.
4.
5.
6.
Figure 11: Stainless Steel Cleaner
7.
TESTS: PART 2
The 4” x 8” hot-dip galvanized surfaces were
divided into 3 sections that were only
contaminated with spray paint, since it was found
in the first part of the study that the other
contaminants were all easily removed. There
were three different colors of spray paint used
(black, red, and yellow) and two different paint
finishes (glossy and matte). In addition, the
contaminated steel was placed outdoors for 48
hours in order to allow the spray paint to develop
a better adhesion to the galvanized surface. Then
three new commercially available cleaning
products were then applied following the
manufacturer’s directions. The surfaces were then
examined to determine how successful each
cleaning product was at removing the spray paint.
PROCEDURE
Take pictures
Spray paint the galvanized panels
Allow to weather for 48 hours
Attempt to clean the galvanized
surface with a single cleaning
product
Rinse surfaces with water and dry
Evaluate the performance of the
cleaning product
Take pictures
•
•
•
•
CONTAMINANTS
Spray Paint:
o Black (matte)
o Red (glossy)
o Yellow (glossy)
CLEANING PRODUCTS
Klean-Strip® Graffiti Remover
Mötsenböcker’s Lift Off 4®
Goo Gone®
TEST RESULTS: PART 2
It was found that when following the
manufacture’s directions, the Klean-Strip®
Graffiti Remover was very successful at removing
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Protecting Steel for Generations
the three different types of spray paint. However,
the Mötsenböcker’s Lift Off 4® was not as
successful when specifically following the
manufacture’s directions, which did not specify
any time between the application and cleaning
processes. When allowing Mötsenböcker’s Lift
Off 4® to sit for approximately 15 minutes on the
galvanized surface before attempting to clean the
surface, the spray paint could then be easily wiped
off.
The third product, Goo Gone®, was
unsuccessful at fully removing the spray paint,
even when attempting many different removal
methods. In Figures 13 - 15, the galvanized plates
after cleaning and the name of the cleaning
product that was used on them are shown.
Figure 13: Klean-Strip® Graffiti Remover
Figure 15: Goo Gone®
TESTS: PART 3
The 4” x 8” galvanized surfaces were again
divided into 3 sections and contaminated with the
three different types of spray paint. This time the
contaminated steel was weathered for 13 days in
order to allow the spray paint to fully adhere to
the galvanized surface. The four best cleaning
products from the first two parts of this study
were then applied following the manufacturer’s
directions. The surfaces were then examined to
determine how successful each cleaning product
was at removing the spray paint. This part of the
test used two galvanized plates for every cleaning
product. In addition, the coating thickness for
each of these galvanized plates was measured
before the spray paint was applied and after they
had been cleaned. This was done in order to
determine if any damage was done to the zinc
coating during the cleaning process. The KleanStrip® Graffiti Remover creates a foam blanket
when initially applied to the galvanized plate and
approximately 20 minutes later, the foam blanket
begins to crack, as shown in Figure 16.
Mötsenböcker’s Lift Off 4® is shown in Figure
17 creating a clear coating when initially applied
and after approximately 10 - 15 minutes, a
reaction occurs between the spray paint and the
cleaner that eventually covers the entire plate.
Figure 14: Mötsenböcker’s Lift Off 4®
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PROCEDURE
1. Choose the top four cleaning
products from parts 1 and 2
2. Take mil readings of the samples
3. Take pictures
4. Spray paint the galvanized panel
5. Allow to weather for 13 days
6. Attempt to clean the galvanized
surface with a single cleaning
product
7. Rinse surfaces with water and dry
8. Evaluate the performance of the
cleaning product
9. Take mil reading of the cleaned
samples
10. Take pictures
•
•
•
•
•
CONTAMINANTS
Spray Paint
o Black (matte)
o Red (glossy)
o Yellow (glossy)
CLEANING PRODUCTS
Klean-Strip® Graffiti Remover
Mötsenböcker’s Lift Off 4®
Goof Off®
Comet®
Figure 16: Approximately 20 Minutes after Application
Figure 17: Approximately 15 Minutes after Application
TEST RESULTS: PART 3
It was again found that the Klean-Strip® Graffiti
Remover and Mötsenböcker’s Lift Off 4® were
very successful at removing all of the spray paint.
The Klean-Strip® Graffiti Remover was allowed
to sit for approximately 20 minutes on the
galvanized surface that is the amount of time
recommended by the manufacture, and then the
paint could be easily wiped off.
The
Mötsenböcker’s Lift Off 4® was allowed to sit for
approximately 15 minutes on the galvanized
surface that is not specifically stated in the
manufacture’s directions, and then the spray paint
could be easily wiped off. The Goof Off® was
successful at removing all of the spray paint once
it was allowed to sit for approximately 20
minutes. However, the overall cleaning process
took much more effort than the cleaning process
for the Klean-Strip® Graffiti Remover or the
Mötsenböcker’s Lift Off 4®. The Comet® was
unsuccessful at completely removing all of the
spray paint, even after attempting many different
removal methods.
The measurement of the coating thickness and the
examination of the galvanized surface helped
determine that none of the cleaning products used
in part 3 of the tests had any major effect on the
coating thickness or integrity.
The coating
thickness measurements can be found in the charts
included in the appendix. In Figures 18 - 21, the
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Protecting Steel for Generations
galvanized plates and the name of the cleaning
product that was used on them are shown.
Figure 18: Klean-Strip® Graffiti Remover
(Plates A & B)
Figure 19: Mötsenböcker’s Lift Off 4® (Plates C& D)
Figure 20: Goof Off® (Plates E & F)
CONCLUSIONS
This study concluded that the two best
commercially available cleaning products that can
be used to remove contaminants from a
galvanized surface are Klean-Strip® Graffiti
Remover and Mötsenböcker’s Lift Off 4®. Both
of these cleaning products are readily available at
local hardware stores and do not cause any
damage to the zinc coating. The Goof Off®
eventually removed all of the spray paint but the
overall cleaning process took much more effort
and it could not be recommended for a vertical
surface. The Comet® worked well on the fresh
paint but would not be recommended on any
weathered contaminants and appeared to have
lightly scratched the zinc surface. These products
all require the use of personal protective
equipment, such as chemical resistant gloves and
safety glasses, and are for outdoor use only. Any
other health and safety recommendations that are
given by the manufacturer must be followed. In
addition, disposal of these products should be
made in accordance with federal, state, and local
regulations. These recommendations can be
found in the product’s MSDS. In Figures 22 - 24,
the Goof Off®, Klean-Strip® Graffiti Remover,
and Mötsenböcker’s Lift Off 4® cleaning
products are shown.
Galvanizers should
recommend that their customers use these
products in order to remove different types of
contaminants from the surface of hot-dip
galvanized steel.
Figure 21: Comet® (Plates G & H)
Figure 22: Goof Off®
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Figure 23: Klean-Strip® Graffiti Remover
Figure 24: Mötsenböcker’s Lift Off 4®
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REFERENCES
1. Material Data Safety Sheet for Klean-Strip® Graffiti Remover by Klean-Strip,
W.M. Barr & Company, INC., 18 of March 2005
(http://www.kleanstrip.com/removers.htm).
2. Material Data Safety Sheet for Mötsenböcker’s Mötsenböcker’s Lift Off 4® 4,
Motsenbocker Advanced Development, Inc., 1 of January 2003,
(http://www.liftoffinc.com).
3. Material Data Safety Sheet for Goofoff, The Valspar Corporation, 31 of August
2005, (http://www.valspar.com/val/resident/goof-off.jsp).
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Protecting Steel for Generations
APPENDIX 1: COATING THICKNESS MEASUREMENTS
Coating Thickness Before and After Cleaning (Sample A)
7.5
7.4
Coating Thickness (mils)
7.3
7.2
7.1
7
Pre
Measurements
6.9
Post
Measurements
6.8
6.7
6.6
6.5
6.4
1
2
3
4
Sample Section
Coating Thickness Before and After Cleaning (Sample B)
3
2.95
Coating Thickness (mils)
2.9
2.85
2.8
2.75
2.7
Pre
Measurements
2.65
Post
Measurements
2.6
2.55
2.5
2.45
1
2
3
4
Sample Section
Coating Thickness Before and After Cleaning (Sample C)
3.5
Coating Thickness (mils)
3.4
3.3
3.2
3.1
Pre
Measurements
3
Post
Measurements
2.9
2.8
2.7
1
2
3
4
Sample Section
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Coating Thickness Before and After Cleaning (Sample D)
3.5
Coating Thickness (mils)
3.4
3.3
3.2
Pre
Measurements
3.1
Post
Measurements
3
2.9
2.8
1
2
3
4
Sample Section
Coating Thickness Before and After Cleaning (Sample E)
3.6
3.5
Coating Thickness (mils)
3.4
3.3
3.2
Pre
Measurements
3.1
Post
Measurements
3
2.9
2.8
1
2
3
4
Sample Section
Coating Thickness Before and After Cleaning (Sample F)
9
8
Coating Thickness (mils)
7
6
5
Pre
Measurements
Post
Measurements
4
3
2
1
0
1
2
3
4
Sample Section
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Coating Thickness Before and After Cleaning (Sample G)
14
Coating Thickness (mils)
12
10
8
Pre
Measurements
6
Post
Measurements
4
2
0
1
2
3
4
Sample Section
Coating Thickness Before and After Cleaning (Sample H)
14
Coating Thickness (mils)
12
10
8
Pre
Measurements
Post
Measurements
6
4
2
0
1
2
3
4
Sample Section
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