FORM OF 6.75% NOTES DUE 2018

Exhibit 4(b)

Unless this certificate is presented by an authorized representative of The Depository Trust Company, a New York Corporation (“DTC”), to Issuer or its agent for registration of transfer, exchange, or payment, and any certificate issued is registered in the name of Cede & Co. or in such other name as is requested by an authorized representative of DTC (and any payment is made to Cede & Co. or to such other entity as is requested by an authorized representative of DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL inasmuch as the registered owner hereof, Cede & Co., has an interest herein.

This Security is a Book-Entry Security within the meaning of the Indenture hereinafter referred to and is registered in the name of a Depositary or a nominee thereof. This Security may not be transferred to, or registered or exchanged for Securities registered in the name of, any Person other than the Depositary or a nominee thereof and no such transfer may be registered, except in the limited circumstances described in the Indenture. Every Security authenticated and delivered upon registration of transfer of, or in exchange for or in lieu of, this Security shall be a Book-Entry Security subject to the foregoing, except in such limited circumstances described in the Indenture.

ALCOA INC.

6.75% Notes Due 2018

Alcoa Inc., a corporation duly organized and existing under the laws of Pennsylvania (herein called the “Company”, which term includes any successor Person under the Indenture referred to on the reverse hereof), for value received, hereby promises to pay to Cede & Co., or registered assigns, the principal sum of              (United States) Dollars on July 15, 2018, and to pay interest thereon from July 15, 2008, or from the most recent January 15 or July 15 (each, an “Interest Payment Date”) to which interest has been paid or duly provided for, semi-annually in arrears on January 15 and July 15 in each year, commencing January 15, 2009, at the rate of 6.75% per annum, until the principal hereof is paid or made available for payment. The interest so payable, and punctually paid or duly provided for, on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on the Regular Record Date for such interest, which shall be the January 1 or July 1 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date. Interest will be paid on the basis of a 360-day year consisting of twelve 30-day months. Except as otherwise provided in the Indenture, any such interest not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of Securities of this series not less than 10 days prior to such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by such exchange, all as more fully provided in said Indenture. Payment of the principal of and any premium and interest on this Security will be made (a) at the Corporate Trust Office of the Trustee or such other office or agency of the Company as may be designated by it for such purpose in the Borough of Manhattan, The City of New York, in such coin or currency of the United States of America as at the time of payment

shall be legal tender for the payment of public and private debts or (b) subject to any laws or regulations applicable thereto and to the right of the Company (limited as provided in the Indenture) to rescind the designation of any such Paying Agent, at the main offices of the Company in Pittsburgh, Pennsylvania, or at such other offices or agencies as the Company may designate, by United States dollar check drawn on, or transfer to a United States dollar account maintained by the payee with, a bank in The City of New York; provided, however, that at the option of the Company payment of interest may be made by United States dollar check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register.

Reference is hereby made to the further provisions of this Security set forth on the reverse hereof, which further provisions shall for all purposes have the same effect as if set forth at this place.

Unless the certificate of authentication hereon has been executed by the Trustee referred to on the reverse hereof, directly or through an Authenticating Agent, by manual signature of an authorized signatory, this Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose.

IN WITNESS WHEREOF, the Company has caused this instrument to be duly executed under its corporate seal.

Dated: July 15, 2008

[SEAL]

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This Security is one of a duly authorized issue of securities of the Company (herein called the “Securities”), issued and to be issued in one or more series under an Indenture, dated as of September 30, 1993 (herein, as supplemented by the First Supplemental Indenture dated as of January 25, 2007 between the Company and the Trustee (as defined below), and the Second Supplemental Indenture dated as of July 15, 2008 between the Company and the Trustee, called the “Indenture”), between the Company and The Bank of New York Mellon Trust Company, N.A., as successor in interest to J. P. Morgan Trust Company, National Association (formerly Chase Manhattan Trust Company, National Association, as successor to PNC Bank, National Association), as Trustee (herein called the “Trustee”, which term includes any successor trustee under the Indenture), to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the Company, the Trustee and the Holders of the Securities and of the terms upon which the Securities are, and are to be, authenticated and delivered. This Security is one of the series designated on the face hereof, initially issued in the aggregate principal amount of (U.S.) $750,000,000.

The Securities of this series are subject to redemption, as a whole or in part, at the option of the Company, at any time or from time to time, on at least 30 days, but not more than 60 days, prior notice to the Holders of the Securities of this series given as described below, at a redemption price equal to the greater of:

“Treasury Rate” means, with respect to any redemption date:

The Treasury Rate will be calculated on the third Business Day preceding the redemption date.

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“Comparable Treasury Issue” means the United States Treasury security selected by an Independent Investment Banker as having a maturity comparable to the remaining term of this Security to be redeemed that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of this Security.

“Independent Investment Banker” means one of the Reference Treasury Dealers, to be appointed by the Company.

“Comparable Treasury Price” means, with respect to any redemption date for this Security:

“Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any redemption date, the average, as determined by the Trustee, of the bid and asked prices for the Comparable Treasury Issue, expressed in each case as a percentage of its principal amount, quoted in writing to the Trustee by such Reference Treasury Dealer at 3:30 p.m., New York City time, on the third Business Day preceding such redemption date.

“Reference Treasury Dealer” means each of Banc of America Securities LLC, Barclays Capital Inc., Citigroup Global Markets Inc., and Lehman Brothers Inc., and their respective successors; provided, however, that if any of the foregoing shall cease to be a primary U.S. Government securities dealer, which is referred to herein as a “Primary Treasury Dealer,” the Company will substitute therefor another nationally recognized investment banking firm that is a Primary Treasury Dealer.

“Remaining Scheduled Payments” means, with respect to each Security to be redeemed, the remaining scheduled payments of the principal thereof and interest thereon that would be due after the related redemption date but for such redemption; provi