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Historic Preservation - Technical Procedures

Spectitle:

Repairing Corrosion Pitting And Cracks In Cast Iron

Procedure code:

0501001R

Source:

Us Custom House/New Orleans, La - Fromherz Engineers, Inc.

Division:

Metals

Section:

Metal Materials

Last Modified:

11/12/2013

Details:

Repairing Corrosion Pitting And Cracks In Cast Iron



REPAIRING CORROSION PITTING AND CRACKS IN CAST IRON


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on using plastic metal
         and weldment to repair corrosion pitting and cracks in
         cast iron.

    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

         3.   Submittals

         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).

1.02 REFERENCES

    A.   American Society for Testing and Materials (ASTM), 
         www.astm.org


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Devcon Corporation
         www.devcon.com

    B.   Belzona, Inc.
         www.belzona.com

    C.   Dumond Chemicals, Inc.
         www.dumondchemicals.com 

    D.   Diedrich Technologies, Inc.
         www.diedrichtechnologies.com 

2.02 MATERIALS

    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
              materials.

    B.   Weldments:  Shall be done in accordance with AWS
         standards.  Cast iron shall be welded with pure nickel
         rods.

    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

2.03 EQUIPMENT

    A.   Wiping cloths

    B.   Eye and skin protection

    C.   Welding equipment

    D.   Electric drill

    E.   Pneunmatic chisel

    F.   Electric Grinder


PART 3---EXECUTION

3.01 PREPARATION

    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
              out.

         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
                   procedure.

         4.   When dry, apply finish coat of paint over the
              patch.

    B.   For smaller pits than those described in A.1. above,
         clean and paint only (see 05010-05-R, 05010-13-S and
         09900-07-S).

    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"
              diameter holes.

         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
         cracks.

                         END OF SECTION
 


cast iron, cast iron corrosion, cast iron pitting, cast iron cracks