Exhibit 4.3


 


 





FOURTH SUPPLEMENTAL INDENTURE, dated
as of December 31, 2017 (the “Fourth Supplemental Indenture”), between ARCONIC INC. (f/k/a Alcoa Inc.), a Pennsylvania
corporation (the “Company”), ARCONIC INC., a Delaware corporation (“New Arconic”), and THE
BANK OF NEW YORK MELLON TRUST COMPANY, N.A., as successor trustee (herein called the “Trustee”).


 


RECITALS OF THE COMPANY


 


The Company and the Trustee are parties
to an Indenture dated as of September 30, 1993 (the “Base Indenture” and as supplemented by the First Supplemental
Indenture dated as of January 25, 2007 and the Second Supplemental Indenture dated as of July 15, 2008, the “Indenture”),
relating to the issuance from time to time by the Company of its Securities. Capitalized terms used herein, not otherwise defined,
shall have the same meanings given them in the Indenture.


 


Section 901(1) of the Base Indenture provides
that a supplemental indenture may be entered into by the Company and the Trustee, without the consent of any Holders, to evidence
the succession of another Person to the Company and the assumption by any such successor of the covenants of the Company in the
Indenture and in the Securities.


 


In connection with that certain Agreement
and Plan of Merger, dated as of October 12, 2017, by and among the Company and New Arconic, a direct wholly owned subsidiary of
the Company, pursuant to which, concurrently with the execution of this Fourth Supplemental Indenture, the Company is being merged
with and into New Arconic, with New Arconic being the surviving corporation in such merger (the “Merger”), the
Company has requested the Trustee to join with it in the execution and delivery of this Fourth Supplemental Indenture in order
to evidence the succession of New Arconic to the Company and the assumption by New Arconic of the covenants of the Company in the
Indenture and in the Securities.


 


The Company has determined that this Fourth
Supplemental Indenture complies with said Section 901 and does not require the consent of any Holders.


 


NOW, THEREFORE, THIS FOURTH SUPPLEMENTAL
INDENTURE WITNESSETH:


 


For and in consideration of the premises
and the purchase of Securities by the Holders thereof, it is mutually agreed, for the equal and ratable benefit of all Holders
of Securities, as follows:


 


I.       ASSUMPTION


 


A. Effective as of the effective time of
the Merger (the “Effective Time”), New Arconic hereby assumes the due and punctual payment of the principal
of (and premium, if any) and interest (including all amounts, if any, payable pursuant to Section 1004 of the Base Indenture) on
all the Securities and performance of every covenant of the Indenture on the part of the Company to be performed or observed.


 






     


     


    

 


B. New Arconic represents and warrants that
it is a corporation organized and validly existing under the laws of Delaware.


 


C. From and after the Effective Time, New
Arconic shall succeed to and be substituted for and may exercise every right and power of the Company under the Indenture with
the same effect as if New Arconic had been named as the Company therein.


 


II.       GENERAL PROVISIONS


 


A. The recitals contained herein shall be
taken as the statements of the Company and New Arconic, and the Trustee assumes no responsibility for the correctness of same.
The Trustee makes no representation as to the validity of this Fourth Supplemental Indenture. The Indenture, as supplemented and
amended by this Fourth Supplemental Indenture, is in all respects hereby adopted, ratified and confirmed.


 


B. This instrument may be executed in any
number of counterparts, each of which so executed shall be deemed to be an original, but all such counterparts shall together constitute
but one and the same instrument.


 


C. The Company hereby certifies that this
Fourth Supplemental Indenture conforms to the current requirements of the Trust indenture Act.


 


D. This Fourth Supplemental Indenture shall
be governed by and construed in accordance with the laws of the Commonwealth of Pennsylvania.


 


E. Henceforth, all references in the Indenture
and the Securities to the “Company” shall be deemed to be references to new Arconic. The Indenture is otherwise ratified
in full.


  


 


[Signature Pages Follow]


 




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	 	ARCONIC INC., a Pennsylvania corporation
	 	 	 
	 	By:	/s/ Peter Hong
	 	Name:	Peter Hong
	 	Title:	Vice President and Treasurer
	 	 	 
	 	 	 
	 	ARCONIC INC., a Delaware corporation
	 	 	 
	 	By:	/s/ Peter Hong
	 	Name:	Peter Hong
	 	Title:  	Vice President and Treasurer


 


 





[Fourth Supplemental Indenture (Arconic
Bonds)]







 




    	 	 	 



     


    

 


 


	 	THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., as Trustee
	 	 	 
	 	By:	/s/ Karen Yu
	 	Name:	Karen Yu
	 	Title:	Vice President


 


 





[Fourth Supplemental Indenture (Arconic
Bonds)]