GGB Gerdau SA

FORM 6-K

U.S. SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE

SECURITIES EXCHANGE ACT OF 1934

Dated March 26, 2015

Commission File Number 1-14878

GERDAU S.A.

(Exact Name as Specified in its Charter)

N/A

(Translation of Registrant’s Name)

Av. Farrapos 1811

Porto Alegre, Rio Grande do Sul - Brazil CEP 90220-005

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F x       Form 40-F o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):o

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):o

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes o             No  x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b):  Not applicable.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused the Report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date:  March 26, 2015

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EXHIBIT INDEX

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Exhibit 99.1

MATERIAL FACT

Gerdau proposes new corporate governance structure

March 26, 2015, Porto Alegre – The Boards of Metalúrgica Gerdau S.A. and Gerdau S.A., following the rules from CVM (Comissão de Valores Mobiliários), propose to their respective Shareholders Meetings, to be held on April 28 and April 29, respectively, the new Boards of Directors composition.

The proposal marks one more phase in the Gerdau Johannpeter family succession process in their business governance. André B. Gerdau Johannpeter, Gerdau Board member and CEO, and Claudio Gerdau Johannpeter, Board member and Executive Vice-president, will also both accumulate the Co-Chairman position in the Gerdau S.A. and Metalúrgica Gerdau S.A. Boards of Directors.

Jorge Gerdau Johannpeter, Chairman of the Boards of Directors of Gerdau S.A. and Metalúrgica Gerdau S.A., and the vice Chairman Germano, Klaus and Frederico Gerdau Johannpeter – will not be part in the proposed Boards of Directors and will be assigned for the Advisory Board to be created. This new Board will have Jorge Gerdau as president, with the support from Germano, Klaus and Frederico, aims to continue to share their strategy and management experiences acquired along the last decades.

The proposal to the shareholders is based in an organized and structured process, following the model realized in the Gerdau Executive Committee succession process occurred in 2007. Furthermore, is important to highlight that Gerdau implemented four generations succession process along the 114 years of history, proving its strong process of governance and management.

Proposal of the new compositions of the Boards of Directors:

Gerdau S.A. Board of Directors

Metalúrgica Gerdau S.A. Board of Directors

Porto Alegre, March 26, 2015.

Andre Pires de Oliveira Dias

Executive Vice President

Investor Relations Director