UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF

THE SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. )

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o Preliminary Proxy Statement

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o Definitive Proxy Statement

þ Definitive Additional Materials

o Soliciting Material Pursuant to §240.14a-12

Kaiser Aluminum Corporation

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

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