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 December 14, 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.

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.

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:  December 14, 2021

EXHIBIT INDEX

Exhibit 99.1

SEIVA S.A. – FLORESTAS E INDÚSTRIAS

Tax ID (CNPJ/ME) 87.043.832/0001-73

Registry (NIRE): 35300521781

NOTICE TO THE MARKET

Gerdau S.A., Metalúrgica Gerdau S.A. and Seiva S.A. – Florestas e Indústrias (collectively, the “Companies”) hereby announce to their shareholders and the market that, in view of the retirement of executive officer Harley Lorentz Scardoelli on December 31, 2021, the meetings of the respective Boards of Directors held on this date deliberated and voted to elect Rafael Dorneles Japur as the Executive Vice-President and Investor Relations Officer of Metalúrgica Gerdau S.A. and Gerdau S.A., effective January 1^st^, 2022, and also to the position of Investor Relations Officer of Seiva S.A. – Florestas e Indústrias.

Rafael Dorneles Japur holds a degree in business administration and a graduate degree in economics from the Federal University of Rio Grande do Sul (UFRGS) and has complete the Advanced Finance Program at Wharton. He began his career at Gerdau in 2005 as an intern and participated in the Planning and Management trainee program. In 2015, he was promoted to Business Development Manager and a year later, he also took on the leadership of the Debt and Capital Markets management functions in the Finance Department. In 2018, he assumed the position of Planning, IT & Innovation Manager at Gerdau Diaco and Gerdau Metaldom in Colombia. In 2020, he returned to Brazil as General Manager - Corporate Finance, with responsibility for Treasury, Debt and Capital Market, Insurance and Mergers & Acquisitions. In 2020, he also served as secretary of Gerdau’s Strategy and Sustainability Committee.

Preparations for this move and the transition between executives were carefully planned to preserve Gerdau’s solid financial health. The transition process is focused on achieving consistent results and maintaining an excellent relationship with shareholders and financial markets.

The Boards of Directors of the Companies thank Harley Lorentz Scardoelli for his important contributions to refining the processes that he led during his 33 years at Gerdau and wish him success in this new phase of his life, with great accomplishments and happiness with his family.

São Paulo, December 14^th^, 2021.

Gustavo Werneck da Cunha

Chief Executive Officer

METALÚRGICA GERDAU S.A.

GERDAU S.A.

Gustavo Werneck da Cunha

Chairman of the Board of Directors

SEIVA S.A. – FLORESTAS E INDÚSTRIAS