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Historic Preservation - Technical Procedures

Spectitle:

Procedures For Soldering Sheetmetal

Procedure code:

0501007R

Source:

Hspg Prepared For Nps - Sero

Division:

Metals

Section:

Metal Materials

Last Modified:

02/24/2012

Details:

Procedures For Soldering Sheetmetal



PROCEDURES FOR SOLDERING SHEETMETAL


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on soldering metal for
         patching damaged or deteriorated sheetmetal roofs and
         gutters.

    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 DEFINITIONS

    A.   Solder--metal or metallic alloy of tin and lead used when
         melted to join metallic surfaces.

1.03 QUALITY ASSURANCE

    A.   Qualifications:  Steel, aluminum and copper systems
         should be applied by qualified sheet metal mechanics
         using methods devised or approved by the manufacturer of
         the metal.  Details may vary depending on the properties
         of the metal, local custom, and architectural effect
         required.


PART 2---PRODUCTS

2.01 MATERIALS  

    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.   Sheetmetal to match remainder of roof or gutters

    B.   Solder

    C.   Soldering flux

    D.   Rosin paper

    E.   Muriatic acid * (generally available in 18 degree and 20
         degree Baume solutions):

         1.   A strong corrosive irritating acid.

         2.   Other chemical or common names include Chlorhydric
              acid; Hydrochloric Acid; Hydrogen chloride; Marine
              acid*; Spirit of salt*; Spirit of sea salt*.

         3.   Potential Hazards:  TOXIC, CORROSIVE TO FLESH;
              CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS,
              FLAMMABLE.

         4.   Available from chemical supply house, drugstore or
              pharmaceutical supply distributor, or hardware
              store.

    F.   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*;
              Solvent naphtha*.

         3.   Potential Hazards:  TOXIC AND FLAMMABLE.

         4.   Safety Precautions:

              a.   AVOID REPEATED OR PROLONGED SKIN CONTACT.

              b.   ALWAYS wear rubber gloves when handling
                   mineral spirits.

              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.

    G.   Clean, soft cloths

2.03 EQUIPMENT

    A.   Chicken ladder, safety belt or harness

    B.   Snips for cutting sheet metal

    C.   Soldering copper, soldering iron

    D.   Handy tongs for bending the edges of the solder

    E.   Metal seamer

    F.   Stiff bristle brushes

    G.   Metal ruler

    H.   Pliers

    I.   Weight (bricks)

    J.   Clamps

    K.   3-5 lb. propane heater for soldering copper or 200 watt
         electric soldering iron

    L.   Heavy gloves and protective gear


PART 3---EXECUTION

3.01 EXECUTION, INSTALLATION, APPLICATION

    NOTE:  USE CAUTION IN HANDLING FLAME TOOLS WHEN SOLDERING.
    THE DANGER OF SETTING THE STRUCTURE ON FIRE IS ALWAYS PRESENT.

    A.   With chemical paint stripper, remove any paint from the
         metal surrounding the patch.  If there's any roofing tar,
         remove it by scraping, followed by scrubbing with
         kerosene, gasoline, or mineral spirits.  

         CAUTION:  THESE SOLVENTS ARE VERY FLAMMABLE

    B.   Clean both the roof and the patch piece by scouring with
         a wire brush or steel wool.

    C.   For Copper:  

         NOTE:  THIS METHOD SHOULD NEVER BE USED TO REPAIR
         FATIGUE-DAMAGED COPPER SHEETMETAL.  SOLDERED PATCHES HAVE
         A DIFFERENT COEFFICIENT OF EXPANSION THAN THE COPPER AND
         WILL EVENTUALLY BREAK AWAY.  SOLDER IS INHERENTLY A WEAK
         ALLOY AND SHOULD BE USED ONLY TO CREATE WATERTIGHT
         JOINTS, NOT WHERE TENSILE OR COMPRESSIVE STRENGTH IS
         NEEDED.  HOWEVER, IT DOES PROVIDE SOME STRENGTH IN
         CONNECTING SHEETS OF COPPER IN "WEIGHTS" LESS THAN 20
         OUNCES.

         1.   Apply muriatic acid for 60 seconds to dissolve any
              oxides.

         2.   Rinse with clean, clear water and wipe dry.

         3.   Paint on liquid non-corrosive rosin flux (zinc
              chloride), applying it ONLY where the solder is to
              go.

         4.   Pre-tin the area by heating with a soldering copper
              and applying a thin coating of solder.

         5.   Apply patch and hold in place with heavy weight, or
              fasten it mechanically with two copper rivets or
              brass nails.  Solder following instructions 4-6
              below.

    B.   For lead-coated copper, tin, tin plate, terneplate:

         1.   Follow instructions for copper, Section 3.01 A.
              above.

         2.   Fasten patches using tinplated cleats or galvanized
              iron or steel nails.

    C.   For galvanized iron or steel:

         1.   Clean with muriatic acid as for copper, Section
              3.01 A.1. and 2. above.

         2.   Because the muriatic acid also acts as the flux,
              after 60 seconds leave acid in place (DO NOT
              RINSE), apply patch, and solder following
              instructions D-F below.  

    D.   Use bar solder that's 50% block tin and 50% pig lead and
         a large soldering copper (typically 1-1/2 lb. or bigger -
         for galvanized iron, use either a 3-5 lb. propane-heated
         soldering copper, or a 200 watt electric soldering iron).
         A home workbench soldering iron won't transmit enough
         heat to the roof to get solder to flow under the patch.

    E.   Use a well-tinned copper to heat the metal and the
         solder.  Let the solder flow into the seams.  If the
         patch is held in with nails or rivets, be sure the solder
         covers their heads.  Apply the solder using a
         noncorrosive rosin flux.  MAKE SURE THE PATCH DOES NOT
         MOVE UNTIL AFTER THE SOLDER COOLS; OTHERWISE, THE SOLDER
         WILL BEGIN TO BREAK.  IF THE PATCH MOVES, START OVER.

    F.   After the solder has cooled, rinse off all excess flux
         with clean water and wipe dry.  If patch is galvanized,
         terne, or tinplate, wipe it down with mineral spirits and
         immediately prime and paint patch to match the remainder
         of the roof.

                         END OF SECTION