Exhibit 5 [Letterhead of Arnold & Porter] February 3, 1999 Armco Inc. One Oxford Centre 301 Grant Street Pittsburgh, Pennsylvania 15219 Ladies and Gentlemen: We refer to the registration statement on Form S-4, Registration No. 333-71203 (the "Registration Statement"), filed by Armco Inc., an Ohio corporation (the "Company"), with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the "Act"), pursuant to which the Company is registering $75,000,000 aggregate principal amount of 8 7/8% Senior Notes due 2008 (the "Exchange Notes"), under an Indenture dated as of November 1, 1993 between the Company and Star Bank, N.A., as trustee (the "Trustee"), as supplemented by Supplemental Indenture No. 1, dated as of November 1, 1993, and Supplemental Indenture No. 2, dated as of December 15, 1998 (the "Indenture"), to be issued in exchange for $75,000,000 aggregate principal amount of the Company's outstanding 8 7/8% Senior Notes due 2008 (the "Exchange Offer"). The terms and conditions of the Exchange Notes and the Exchange Offer are as set forth in the Registration Statement and the prospectus (the "Prospectus") contained therein. We have examined originals or copies, certified or otherwise identified to our satisfaction, of the Registration Statement, the Indenture, the form of Exchange Notes set forth in the Indenture, and such corporate records, agreements, documents and other instruments, and such certificates or comparable documents of public officials and of officers and representatives of the Company, and have made such inquiries of such officers and representatives as we have deemed relevant and necessary as a basis for the opinions hereinafter set forth. Based upon and subject to the foregoing, we are of the opinion that the Exchange Notes have been duly authorized by the Company and when the Exchange Notes have been duly executed by the Company and authenticated by the Trustee in accordance with the terms of the Indenture and issued in exchange for the Old Notes in accordance with the terms of the Exchange Offer, the Exchange Notes will constitute valid and binding obligations of the Company under the laws of the State of New York, subject to bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium, receivership and similar laws relating to or affecting creditors' rights generally and to equitable principles (regardless of whether enforcement is sought in a proceeding in equity or at law). The foregoing opinion is limited to the laws of the State of New York and, in reliance upon the opinion of Gary R. Hildreth, General Counsel of the Company, an executed copy of which is attached hereto (the "Hildreth Opinion"), the laws of the State of Ohio, and we do not express any opinion herein concerning the laws of any other jurisdiction. To the extent the foregoing opinion relates to matters governed by the laws of the State of Ohio, such opinion is subject to the qualifications and limitations expressed in the Hildreth Opinion. We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the reference to this firm under the heading "Legal Matters" in the Registration Statement. In giving the foregoing consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission thereunder. This opinion is solely for your information and is not to be quoted in whole or in part, summarized or otherwise referred to without our written consent, except as provided in the preceeding paragraph. This opinion is as of the date hereof. We disclaim any responsibility to update or supplement this opinion to reflect any events or state of facts which may hereafter come to our attention or any changes in statutes or regulations or any court decisions which may hereafter occur. Very truly yours, /s/ ARNOLD & PORTER Attachment to Exhibit 5 [Letterhead of Armco] February 3, 1999 Arnold & Porter 399 Park Avenue New York, New York 10022 Ladies and Gentlemen: I refer to the registration statement on Form S-4, Registration No. 333-71203 (the "Registration Statement"), filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the "Act"), pursuant to which Armco Inc., an Ohio corporation (the "Company"), is registering $75,000,000 aggregate principal amount of 8 7/8% Senior Notes due 2008 (the "Exchange Notes"), under an Indenture dated as of November 1, 1993 between the Company and Star Bank, N.A., as trustee (the "Trustee"), as supplemented by Supplemental Indenture No. 1, dated as of November 1 1993, and Supplemental Indenture No. 2, dated as of December 15, 1998 (the "Indenture"), to be issued in exchange for $75,000,000 aggregate principal amount of the Company's outstanding 8 7/8% Senior Notes due 2008 (the "Exchange Offer"). The terms and conditions of the Exchange Notes and the Exchange Offer are as set forth in the Registration Statement and the prospectus (the "Prospectus") contained therein. I have examined originals or copies, certified or otherwise identified to my satisfaction, of the Registration Statement, the Indenture, the form of Exchange Notes set forth in the Indenture, and such corporate records, agreements, documents and other instruments, and such certificates or comparable documents of public officials and of officers and representatives of the Company, and have made such inquiries of such officers and representatives as I have deemed relevant and necessary as a basis for the opinions hereinafter set forth. Based upon and subject to the foregoing, I am of the opinion that the Exchange Notes have been duly authorized by the Company. The foregoing opinion is limited to the laws of the State of Ohio and I express no opinion herein concerning the laws of any other jurisdiction. I hereby consent to the filing of this opinion as an exhibit to the Registration Statement and/or as an attachment to your opinion being filed as an exhibit to the Registration Statement (and in this regard I consent to your reliance on this opinion) and to be named under the caption "Legal Matters" in the Prospectus forming part of the Registration Statement. In giving this consent, I do not thereby admit that I am within the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission thereunder. Very truly yours, /s/ Gary R. Hildreth Gary R. Hildreth General Counsel