1 General Provisions
1.0.1 This standard is formulated in order to implement the national relevant principles and policies, uniform technical criteria, actively adopt new process, new material, new structure and new technology in the corrosion control for steel pipeline (hereinafter referred to as "pipeline") and steel storage tank (hereinafter referred to as "tank") , and achieve technical advancement, economic rationality, safety and usability and high quality.
1.0.2 This standard is applicable to newly-built, extended and rebuilt internal and external corrosion control for pipeline and tank which are intended to transmit and store crude oil, refined oil, natural gas and water (including sewage) with the temperature less than 100℃ on land corrosive environment. It is not applicable to corrosion control in marine corrosive environment.
1.0.3 Design of corrosion control for pipeline and tank shall not only meet those specified in this standard but also the current relevant mandatory standards in China.
2 Terms
2.0.1 Corrosive environment
Environment where one or more corrosive factors are available.
2.0.2 Corrosion rate
Corrosion loss for metals in unit time.
2.0.3 Coating
Protective layer on the metal surface intended to isolate the metal surface with the surrounding environment to inhibit corrosion. It is classified into insulated coating (also anti-corrosive insulation, anti-corrosive coating for short) and non-insulated coating (e.g. plating) according to its coating.
2.0.4 Cathodic protection
Electrochemical protection reached by reducing corrosion potential, generally including impressed current protection and sacrificial anode protection.
2.0.5 Impressed current
Current applied through external power supply, also referred to as impressed current.
2.0.6 Sacrificial anode
Metal electrode which provides cathodic protection current and connected with the protected body in the medium of ionic conduction. In the soil environment, mg-based sacrificial anode and Zn-based sacrificial anode are used usually.
2.0.7 DC interference
Change of corrosion potential of buried metal structure under the action of DC stray current in earth. It is occurs in anodic field, it is called anodic interference and if it occurs in cathodic field, it is called cathodic interference.
2.0.8 AC interference
Variance in voltage and current of adjacent pipeline generated by AC line and equipment. It is classified into instant interference, persistent interference and intermittent disturbance according to interference time.
2.0.9 Insulated joint
Pipeline connection mode taken in order to cut off longitudinal current of pipeline, including insulation flange joint and insulated joint.
2.0.10 Bond
A kind of metal mold connection, intended to control the current exchange among the metal structure, including interference bond, voltage equalizing bond and continuity bond.
2.0.11 Polarization potential
Potential at metal structure /electrolyte interface, the sum of corrosion potential and cathodic polarization.
3 Basic Requirements
3.0.1 The following factors shall be considered before determining whether the corrosion control is needed for pipeline and tank:
1 Records of corrosion detection, operation record and visual examination;
2 Results of examination test for other similar system and environment;
3 Project design standards and safety and economy.
Foreword I
1 General Provisions
2 Terms
3 Basic Requirements
4 Anti-corrosion Coating
5 Cathodic Protection
5.1 General Requirements
5.2 Cathodic Protection Criteria
5.3 Electrical Insulation
5.4 Electrical Continuity
5.5 Testing Point of Corrosion Control
5.6 Design of Cathodic Protection
6 Interference Corrosion Control
6.1 DC Interference
6.2 AC Interference
7 Corrosion Control Investigation and Record
Explanation of Wording
