6-K

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 August 20, 2021

Commission File Number 1-14878

GERDAU S.A.

(Exact Name as Specified in its Charter)

N/A

(Translation of Registrant’s Name)

Av. Dra. Ruth Cardoso, 8,501 – 8° andar

São Paulo, São Paulo - Brazil CEP 05425-070

(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   ¨

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): ¨

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): ¨

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 ¨     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:  August 20, 2021

EXHIBIT INDEX

Exhibit 99.1

NOTICE TO THE MARKET

Gerdau S.A. and Metalúrgica Gerdau S.A. (jointly, the “Companies”) inform their shareholders and the general market that, on August 18, 2021, the Board of Directors of Gerdau S.A. approved the corporate reorganization involving its Mexican subsidiary Sidertúl, S.A. de C.V. (“Sidertúl”) and the companies Aceros Corsa, S.A. de C.V. (“Aceros Corsa”) and Gerdau Corsa, S.A.P.I. de C.V. (“Gerdau Corsa”), both also located in Mexico and jointly controlled by the Companies with the group formed by Corcre, S.A.P.I. de C.V. and Juan Angel Córdova Creel (jointly, “Grupo Córdova”).

The corporate reorganization approved by the Board of Directors involves the merger of the companies Sidertúl and Aceros Corsa by Gerdau Corsa (“Merger”) and is part of the process to reorganize and simplify the ownership structure in Mexico, with the objective of (i) strengthening the financial structure of Gerdau Corsa, with reductions in its leverage and financial expenses; (ii) centralize the main business activities to capture operating efficiency gains at the companies involved; and (iii) optimize internal processes to capture synergies and economies of scale to reduce administrative, operational and tax costs.

As a preliminary step in the Merger, Grupo Córdova will acquire 16.84% of the share capital of Sidertúl, for US$ 32,500,000 to equalize its equity interest in the share capital of Gerdau Corsa after the Merger (“Purchase and Sale”).

As a result of the Purchase and Sale and of the Merger, Gerdau S.A. will increase, indirectly, its interest in the share capital of Gerdau Corsa from 70% to 75%, maintaining its shared control of Gerdau Corsa with Grupo Córdova. The corporate reorganization also will reinforce the commitment of the Companies with respect to their operations in Mexico, an important and strategic market for their long-term vision.

The consummation of the Purchase and Sale and of the Merger, which is expected to be concluded in the fourth quarter of 2021, is subject to approval by the shareholders of the companies involved and by Mexico's antitrust agency, Comisión Federal de Competencia Económica (COFECE), and to other conditions typical to this type of corporate reorganization.