Foreword a. This recommended practice is under the jurisdiction of the API Committee on Standaridization of Tubular Goods. b. The statements on corrosion of casing and tubing as given herein@ were developed with the cooperation of the Technical Products Committee on Corrosion of Oil and Gas Well Equipment@ National Association of Corrosion Engineers. c. Other specifications and recommended practices under the jurisdiction of the API Committee on Standardization of Tubular Goods include the following: 5A: Specification for Casing@ Tubing@ and Drill Pipe. Covers seamless steel drill pipe@ and seamless and welded steel@ open-hearth iron@ and wrought-iron casing and tubing in various grades. Processes of manufacture@ chemical and physical requirements@ methods of test@ and dimensions are included@ also thread and gage dimensions@ gaging practice@ and requirements on couplings and thread protectors. 5B: Specification for Inspection of External and Internal Pipe Threads. Covers methods of inspecting internal and external pipe threads and descriptions of instruments for measuring thread elements. 5L: Specification for Line Pipe. Covers seamless and welded steel@ seamless and welded open-hearth iron@ and welded wrought-iron line pipe in various grades. It includes standard-weight threaded line pipe; and standard weight@ regular-weight@ special@ extra-strong@ and double-extra-strong@ plain-end line pipe. Processes of manufacture@ chemical and physical requirements@ methods of test@ and dimensions are included; also thread and gage dimensions@ gaging practice@ and requirements on couplings and thread protectors. 5LX: Specification for High-Test Line Pipe. Covers various grades of seamless and welded steel line pipe having greater tensile and bursting strengths and subject to more vigorous testing than for pipe manufactured under API Std 5L. Processes of manufacture@ chemical and physical requirements@ methods of test and dimensions are included. 5A: Bulletin on Obsolete Sharp Threads for Casing and Tubing. Covers dimensional data for casing and tubing sharp threads@ now superseded by round-form threads. 5A1: Bulletin on High-Strength Casing Joints. Covers minimum performance properties of proposed API high-strength casing joints. 5A2: Bulletin on High-Pressure Thread Compounds. Covers the formulation@ process of manufacture@ and labeling of thread compounds for high-pressure oil-field services. 5C2: Bulletin on Performance Properties of Casing and Tubing. Covers collapsing pressures@ internal yield pressures@ and joint strengths of casing and tubing conforming to API Std 5A. d. No recommendations on materials for use as thread compounds are given herein. It is suggested that the selection of a thread compound be given careful consideration by the user bearing in mind that a satisfactory compound should possess certain properties@ the major of which are (1) to lubricate the thread surface to facilitate joint make-up and break-out without galling@ and (2) to seal voids between the mating thread surfaces and effectively prevent leakage. Compounds which have given outstanding service under both laboratory and field conditions are described in API Bul 55A2. e. No recommendations are given herein on materials@ chemicals or coatings for the protection of tubular products from corrosion or the control of corrosive conditions. Several organizations are actively investigating such corrosion problems and it is suggested that use be made of the latest information available on this subject.