<PAGE>

                                                                    EXHIBIT 10.6

                        FOURTH AMENDMENT AND AGREEMENT TO
            CONSIGNMENT, FORWARD CONTRACTS AND TRADING LINE AGREEMENT

      This FOURTH AMENDMENT AND AGREEMENT TO CONSIGNMENT, FORWARD CONTRACTS AND
TRADING LINE AGREEMENT is made as of March 27, 2003, by and between FLEET
PRECIOUS METALS INC., a Rhode Island corporation with offices at 111 Westminster
Street, Providence, Rhode Island 02903 ("FPM"), and WOLVERINE TUBE, INC., a
Delaware corporation with its principal place of business at 200 Clinton Avenue,
Suite 1000, Huntsville, Alabama 35801 ("WOLVERINE TUBE"), WOLVERINE TUBE
(CANADA) INC., an Ontario corporation with its principal place of business at
200 Clinton Avenue, Suite 1000, Huntsville, Alabama 35801 ("WOLVERINE CANADA"),
and WOLVERINE JOINING TECHNOLOGIES, LLC, a Delaware limited liability company
and successor by merger to WOLVERINE JOINING TECHNOLOGIES, INC., a Delaware
corporation with its principal place of business at 235 Kilvert Street, Warwick,
Rhode Island 02886 ("WOLVERINE JOINING") (Wolverine Tube, Wolverine Canada and
Wolverine Joining are hereinafter sometimes referred to individually as a
"COMPANY" and collectively as the "COMPANIES").

                                WITNESSETH THAT:

      WHEREAS, FPM and Wolverine Tube, Wolverine Canada and Wolverine Joining
are parties to a certain Consignment, Forward Contracts and Trading Line
Agreement dated as of March 28, 2001, as previously amended (as amended, the
"Consignment, Forward Contracts and Trading Line Agreement") pursuant to which
FPM agreed to extend certain consignment and other credit facilities to
Wolverine Tube, Wolverine Canada and Wolverine Joining, on the terms and
conditions contained therein; and

      WHEREAS, the parties hereto desire to amend the Consignment, Forward
Contracts and Trading Line Agreement as hereinafter provided;

      NOW, THEREFORE, for value received, and for other good and valuable
consideration, the receipt and adequacy of which are hereby acknowledged, the
parties hereto hereby agree as follows:

      1.    All capitalized terms used herein without definition shall have the
meanings assigned by the Consignment, Forward Contracts and Trading Line
Agreement.

      2.    Effective the date hereof, Paragraph 7.10 of the Consignment,
Forward Contracts and Trading Line Agreement is amended in its entirety to read
as follows:

            "7.10. Minimum Consolidated EBITDA. Consolidated EBITDA for the
      Consolidated Parties shall at all times be greater than or equal to the
      following amounts for the indicated fiscal quarter, calculated on a
      rolling four quarter basis (except for the fiscal quarter ending March 31,
      2002, Consolidated EBITDA shall be calculated only for such quarter, for
      the fiscal quarter ending June 30, 2002, Consolidated EBITDA shall be
      calculated for the two fiscal quarters then ending and for the fiscal
      quarter ending

<PAGE>

September 30, 2002, Consolidated EBITDA shall be calculated for the three fiscal
quarters then ending):

<TABLE>
<CAPTION>
                                                              Minimum Consolidated
         Fiscal Quarter Ending                                       EBITDA
-----------------------------------------------               --------------------
<S>                                                           <C>
March 31, 2002                                                    $ 7,800,000
June 30, 2002                                                     $21,500,000
September 30, 2002                                                $34,500,000
December 31, 2002                                                 $45,000,000
March 31, 2003                                                    $40,000,000
June 30, 2003                                                     $40,000,000
September 30, 2003                                                $40,000,000
December 31, 2003                                                 $42,000,000
Each fiscal quarter ending in fiscal year 2004                    $55,000,000
</TABLE>

      3.    All necessary conforming changes to the Consignment, Forward
Contracts and Trading Line Agreement necessitated by reason of this Fourth
Amendment and Agreement to Consignment, Forward Contracts and Trading Line
Agreement shall be deemed to have been made.

      4.    All references to the "Consignment, Forward Contracts and Trading
Line Agreement" in all documents or agreements by and between the parties
hereto, shall from and after the effective date hereof refer to the Consignment,
Forward Contracts and Trading Line Agreement, as previously amended and as
amended hereby, and all obligations of the Companies under the Consignment,
Forward Contracts and Trading Line Agreement, as previously amended and as
amended hereby, shall be secured by and be entitled to the benefits of such
other documents and agreements.

      5.    Except as amended hereby, the Consignment, Forward Contracts and
Trading Line Agreement shall remain in full force and effect and is in all
respects hereby ratified and affirmed.

      6.    The Companies jointly and severally covenant and agree to pay all
out-of-pocket expenses, costs and charges incurred by FPM (including reasonable
fees and disbursements of counsel) in connection with the preparation and
implementation of this Fourth Amendment and Agreement to Consignment, Forward
Contracts and Trading Line Agreement Agreement. The Companies also jointly and
severally covenant and agree to pay promptly all taxes and recording and filing
fees payable under applicable law with respect to the amendment effected hereby.

      7.    This Fourth Amendment and Agreement to Consignment, Forward
Contracts and Trading Line Agreement may be executed in separate counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument.

                       *THE NEXT PAGE IS A SIGNATURE PAGE*

                                      -2-

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      IN WITNESS WHEREOF, the undersigned parties have caused this Fourth
Amendment and Agreement to be executed by their duly authorized officers as of
the date first above written.

WITNESS:                           WOLVERINE TUBE, INC.

/s/ Mary Ann Michetti              By: /s/ James E. Deason
---------------------                  -----------------------------------------
                                   Title: Executive V.P., CFO and Secretary

                                   WOLVERINE TUBE (CANADA) INC.

/s/ Mary Ann Michetti              By: /s/ James E. Deason
---------------------                  -----------------------------------------
                                   Title: Executive V.P. and Secretary-Treasurer

                                   WOLVERINE JOINING TECHNOLOGIES, LLC,


/s/ Mary Ann Michetti              By: /s/ James E. Deason
---------------------                  -----------------------------------------
                                   Title: Vice President

                                   FLEET PRECIOUS METALS INC.

                                   By: /s/ John C. Schmitt II
                                       -----------------------------------------
                                   Title: Vice President

                                   By: /s/ Fredrick W. Reinhardt
                                       -----------------------------------------
                                   Title: Senior Vice President

                                      -3-