Removing Paint From Wrought Iron, Cast Iron And Steel Using Thermal Methods
- Procedure code:
- Developed For Hspg (Nps - Sero)
- Metal Materials
- Last Modified:
REMOVING PAINT FROM WROUGHT IRON, CA= ST IRON AND STEEL USING
THE CLEANING OR STRIPPING OF METALS MAY INVOLVE THE USE OF
ABRASIVES, LIQUIDS OR SOLVENTS WHICH MAY SPLASH OR RUN OFF ONTO
ADJACENT MATERIALS. TAKE SPECIAL CARE TO PROTECT ALL ADJACENT
MATERIALS, AND DO NOT USE THIS PROCEDURE ON METALS OTHER THAN
SPECIFIED IN THE SUMMARY.
BEFORE UNDERTAKING ANY PROJECT INVOLVING PAINT REMOVAL, APPLICABLE
STATE AND FEDERAL LAWS ON LEAD PAINT ABATEMENT AND DISPOSAL MUST
TAKEN INTO ACCOUNT AND CAREFULLY FOLLOWED. STATE AND FEDERAL
REQUIREMENTS MAY AFFECT OPTIONS AVAILABLE TO OWNERS ON BOTH PAINT
REMOVAL AND REPAINTING. THESE LAWS, AS WELL AS ANY REQUIREMENTS
PROHIBITING VOLATILE ORGANIC COMPOUNDS (VOCs), REGULATORY
INFORMATION CAN BE REQUESTED FROM THE ENVIRONMENTAL
PROTECTION AGENCY (EPA) REGIONAL OFFICE AND/OR THE STATE OFFICE OF
(For reference see National Park Service Preservation Brief 28, "Painting Historic Interiors".)
A. This procedure includes guidance on the selection of
appropriate thermal methods of paint and rust removal
from wrought iron, cast iron and steel. These metals
should be repainted immediately following paint removal
in order to prevent exposure to the atmosphere and
B. For information on painting and coating these materials
see 05010-13-S "Primers and Paints for Wrought Iron, Cast
Iron and Steel", 05010-18-R "Applying a Sacrificial
Coating to Wrought Iron, Cast Iron and Steel", and 09900-07-S
"General Guidelines for Painting Exterior and
C. Thermal methods as used herein shall apply to high
velocity oxyacetylene or oxypropane flame cleaning, a
standard surface preparation method for steel and cast
iron, or to the heat gun.
1. The heat gun works using a hot blast of air at 500
to 750 degrees Fahrenheit. Extreme caution should
be taken when using this method.
a. Heat higher than 1100 degrees fahrenheit will
vaporize lead paint and is hazardous.
b. The hot air blast produced by the heat gun can
ignite debris within a wall cavity or behind a
cornice or soffit. The dust can smolder only
to ignite hours later after the work crew has
gone home so extreme caution must be taken
when using this method.
c. As with flame cleaning, the hot air of a heat
gun can overheat cast iron and steel features
creating localized thermal stresses, or
causing small sections to become distorted.
D. There are several causes for paint failure on metal.
Excess moisture can cause rusting. As metal rusts, the
rust expands breaking the bond between the metal and the
paint. Inadequate or improper surface preparation can
interfere with the proper bonding of the new paint. The
wrong primer can cause anything from pitting of the metal
surface to peeling of the new paint.
E. It is not necessary to remove all previous coats of paint
1. they are adhering soundly,
2. the new painting system is compatible,
3. important design details are not being obscured by
the paint layers.
F. An archives of the paint history of the building is to be
maintained. This is to include the paint samples taken
during research, samples of the new paint colors and the
manufacturers technical information.
G. Safety Precautions:
1. Make sure that a fire extinguisher is readily
available in case of emergency.
2. No food or drink shall be allowed near any work
station so as to prevent contamination from paint,
paint chips or paint dust which may contain lead
and other toxic substances.
3. PAINT BEING REMOVED MAY CONTAIN LEAD. ALL WORKMEN
MUST WEAR PROTECTIVE CLOTHING, (INCLUDING HAIR),
GOGGLES AND RESPIRATORS WITH PROPER FILTERS.
4. Protective clothing shall be removed at the end of
each day and kept at the site to prevent workers
from taking dust and paint chips to other parts of
the site or to their homes.
5. Wash hands and face often, especially before eating
and at the end of the day.
H. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
I. For additional information on cast and wrought iron see
the following HBPP procedures:
1. 05010-04-S, "Cast Iron: Characteristics, Uses and
2. 05010-11-S, "Wrought Iron: Characteristics, Uses
3. 05010-01-S, "Checklist for Inspecting Cast Iron
NOTE: Chemical products are sometimes sold under a common
name. This usually means that the substance is not as pure as
the same chemical sold under its chemical name. The grade of
purity of common name substances, however, is usually adequate
for stain removal work, and these products should be purchased
when available, as they tend to be less expensive. Common
names are indicated below by an asterisk (*).
A. Mineral Spirits:
1. A petroleum distillate that is used especially as a
paint or varnish thinner.
2. Other chemical or common names include Benzine*
(not Benzene); Naphtha*; Petroleum spirits*;
3. Potential Hazards: TOXIC AND FLAMMABLE.
4. Safety Precautions:
a. AVOID REPEATED OR PROLONGED SKIN CONTACT.
b. ALWAYS wear rubber gloves when handling
c. If any chemical is splashed onto the skin,
wash immediately with soap and water.
5. Available from construction specialties
distributor, hardware store, paint store, or
printer's supply distributor.
B. Soft, clean rags
A. High velocity oxyacetylene or oxypropane flame.
B. Heavy duty electric heat gun with metal case. Operating
temperature between 500 and 750 degrees Fahrenheit.
A number of replacement heat elements
should also be kept on hand.
C. A variety of putty knives and paint scrappers of
different shapes and flexibility.
D. Proper, heavy-duty extension cords are required.
E. Power Supply: Heat guns draw approximately 15 amps of
power. Each work station is to be provided with its own
temporary power supply so as not to overload other
A. Before work is begun on removing the existing paint film
or otherwise preparing the surface all sources of excess
moisture shall be inspected and repaired or replaced as
1. Protect adjacent surfaces, including grass, shrubs
and trees with paper, drop cloths and other means.
Items not to be painted which are in contact with
or adjacent to painted surfaces shall be removed or
protected prior to surface preparation and painting
2. All waste material shall be collected at the end of
each work day and properly disposed of. It is
considered Hazardous Waste.
3. Work area shall be sealed to prevent the spread of
dust and debris beyond the work site.
4. After paint removal is complete, area shall be
vacuumed with machines equipped with HEPA (High
Efficiency Particulate Air) filters to insure all
lead dust has been removed.
3.03 ERECTION, INSTALLATION, APPLICATION
NOTE: REMOVE ONLY AS MUCH PAINT AND RUST EACH DAY AS CAN BE
PRIMED THAT SAME DAY. BARE IRON AND STEEL WILL BEGIN TO RUST
AGAIN WITHIN A MATTER OF HOURS. IT SHOULD NOT BE ALLOW= ED TO
SIT UNPROTECTED OVERNIGHT.
A. Flame cleaning:
NOTE: FLAME CLEANING MUST BE PERFORMED BY AN EXPERIENCED
OPERATOR FOR IF DONE TOO SLOWLY LOOSE SCALE AND OTHER
FOREIGN MATERIAL CAN BE FUSED TO THE METAL RATHER THAN
REMOVED FROM IT.
1. Flame cleaning may be executed under both damp or
wet conditions and will help dry the surface.
2. Flame cleaning is NOT recommended on cast iron
because of thermal stresses which can be created by
overheating in localized areas. Nor is it
recommended for thin sections of steel or wrought
iron, i.e. window sash and frame members, because
of the danger of distorting the metal.
B. Heat gun:
NOTE: A HEAT GUN MAY BE OF LIMITED USE IN REMOVING PAINT
FROM CAST IRON AND STEEL. TESTING SHOULD BE DONE USING
THERMAL, ABRASIVE AND CHEMICAL METHODS TO DETERMINE WHICH
IS THE MOST EFFICIENT WHILE PRESERVING THE METAL
1. Aim nozzle at painted surface until the paint
begins to bubble.
2. Using scrapers or dental picks or other similar
tools remove paint before it begins to cool.
CAUTION: DO NOT HOLD GUN TO ANY ONE AREA FOR AN
EXTENDED PERIOD OF TIME TO AVOID OVERHEATING THE
3. Using a clean, soft cloth, wipe the surface with
mineral spirits to remove all residue.
END OF SECTION