Repairing Corrosion Pitting And Cracks In Cast Iron
REPAIRING CORROSION PITTING AND CRACKS IN CAST IRON
A. This procedure includes guidance on using plastic metal
and weldment to repair corrosion pitting and cracks in
B. 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).
A. American Society for Testing and Materials (ASTM),
A. Devcon Corporation
B. Belzona, Inc.
C. Dumond Chemicals, Inc.
D. Diedrich Technologies, Inc.
A. Plastic Metal Material: Two-part product composed of a
silicone/steel alloy blended with a high molecular weight
polymer, such as "Plastic Steel 5 Minute Putty (SF)" (Devcon Corporation),
Belzona IIII "Super Metal" (Belzona, Inc.), or approved equal.
1. Material shall be machinable grade after curing, of
a paste consistency having negligible slump at a 1"
thickness or less.
2. Material shall show no evidence of measurable
shrinkage from plastic state to hardened state.
3. Cured material shall show no visible signs of
corrosion after 5000 hours exposure in ASTM B 117
salt spray testing procedure.
4. Submit samples of the two components of the plastic
metal material, prior to mixing. Also submit
samples of the completed, cured plastic metal
B. Weldments: Shall be done in accordance with AWS
standards. Cast iron shall be welded with pure nickel
C. Chemical Stripper: "Peel Away 1" (Dumond Chemicals, Inc.),
"404 Rip Strip" (Diedrich
Technologies, Inc.), or approved equal.
D. Emery paper
E. 600 grit aluminum oxide paper
A. Wiping cloths
B. Eye and skin protection
C. Welding equipment
D. Electric drill
E. Pneunmatic chisel
F. Electric Grinder
A. Surface Preparation:
1. Surface preparation shall be done under the
supervision of the RHPO.
2. The RHPO will designate sample areas for testing of
surface preparation on the various different
components that require repair. No other surface
preparation is to be done until sample areas have
been approved. Approved areas shall become the
standard of comparison for all surface preparation
work. Protect from weathering, but do not alter or
opaquely cover sample areas until all preparation
work has been completed and approved.
3. The time interval between final cleaning and
application of primer shall not exceed two hours.
Prime coat shall be applied prior to application of
plastic metal materials. Allow 48 hours between
application of prime coat and application of
plastic metal material.
4. See 05010-05-R for cleaning of metal surfaces which
receive plastic metal repairs.
3.02 ERECTION, INSTALLATION, APPLICATION
A. For corrosion pitting larger than 1/4" in diameter with
a depth of at least 1/8":
1. Abrasively clean with sandpaper the pit and
surrounding materials until all evidence of paint
and corrosion is gone and a "white metal" condition
is achieved. If the RHPO judges that the area
cannot be adequately cleaned it shall be ground
2. Prime paint the area immediately (see 05010-13-S
and 09900-07-S for guidance).
3. Carefully and completely fill the corrosion pit
with plastic metal no sooner than 48 hours after
prime painting and allow to dry.
a. When accessible from both faces of components,
fill holes and cracks and build up the missing
portions of component from each face utilizing
a temporary form as a backing.
b. Temporary form shall be polyethylene or be
faced with polyethylene or other similar
material to which plastic metal will not
adhere. Do not remove temporary form until
the plastic metal has cured to the extent
recommended by the manufacturer.
c. If filling from the opposite side is not
accomplished within the time limits
recommended by the manufacturer, grind out the
material that has been placed and repeat the
4. When dry, apply finish coat of paint over the
B. For smaller pits than those described in A.1. above,
clean and paint only (see 05010-05-R, 05010-13-S and
C. For Non-structural Open Cracks in Existing Cast Iron
Components: HAIRLINE CRACKS SHOULD NOT BE OPENED
1. Abrasively clean the area along and in the
immediate vicinity of the crack until all evidence
of paint and corrosion is gone and a "white metal"
condition is achieved. Cleaning shall extend a
minimum of 4" beyond the visible ends of the crack.
2. Drill a 1/2" diameter hole at the ends of the crack
and grind out a 1/4" wide, full depth vee groove
along the path of the crack, between the two 1/2"
3. Immediately prime paint the area (see 05010-05-R,
05010-13-S and 09900-07-S).
4. Carefully and completely fill the groove and two
holes with plastic metal. Finish the surface
smooth and flush with the surrounding base metal.
D. Repair of Deep Corrosion Pitting Using Weldment: Follow
the procedures outlined in Section A. above, except use
weldment instead of plastic metal to fill holes and
END OF SECTION