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Galvanically Induced Hydrogen Stress Cracking (GHSC)

GHSC电偶腐蚀试验

Project Name

Galvanically Induced Hydrogen Stress Cracking (GHSC)

Test Purpose

Examine the corrosion resistance ability of products and metal material in acid environment

Test Object

Petroleum Pipeline, Pressure Vessel, Boiler, Liquid Gas Storage Tank, Valve, Flange, Weld, Carbon Steel, Stainless Steel and other metal material & products

 

Project Introduction

Actually, galvanic corrosion is a kind of macroscopic corrosion cell, and generating galvanic corrosion should have the following three basic conditions:

① Existing ionic conduction branch: For most of galvanic corrosion, corrosion electrolyte mainly refers to the water film or solution condensing on the surface of material, which contains some impurities (such as chloride, sulfate and others). Corrosion electrolyte must exist continuously between different materials to constitute the ionic conduction branch of a corrosion cell.

② Existing the materials having different corrosion potential: The corrosion potential difference between two materials is the driving force of galvanic corrosion.

③ Existing electronic conduction branch: Two different metal materials contact directly or through other conductor to constitute the electronic conduction branch of galvanic corrosion cell。

The methods to prevent galvanic corrosion:

(1) Try to avoid the electronic contact between dissimilar metals having great disparity in electronic potential difference。

(2) Avoid the negative area ration of large cathode and small anode, the components having small area should be made from the metal having positive corrosion potential。

(3) If the dissimilar metals having great disparity in electronic potential difference are assembled together, the insulation slices should be added to the middle of the dissimilar metals generally, and the slices should be tighten and non-hygroscopic to avoid forming crevice corrosion。

(4) The anode component should be easy to be replaced or thickened to extend life when designing.

(5) Add corrosion inhibitor or coating on the metal surface to reduce the corrosion of medium, or add a third metal to form cathodic protection, etc., if possible.

GHSC test should be performed according to requirements and meet the following additional requirements, selection and instructions. A) The CRA sample forms a galvanic couple with the unalloyed steel (carbon steel) completely immersed in test solution. According to NACE TM0177-1996,the area ratio of CRA sample and unalloyed steel should be 0.5~1, and the loading fixture shall be electric insulation with CRA sample and carbon steel coupled. For the assessing of specific application, CRA can be coupled with low alloy material which will be coupled with CRA in using. B) The test environment is the solution A according to NACE TM0177-1996, the partial pressure of H2S is 0.1MPa, and the temperature is 24℃±3℃. For the assessing of specific application, the SSC test environment described in E2.5 can be used.

  Test Methods and Standards

NACE TM0177-1996

Method A: Standard Tensile Test

Method B: Standard Bending Beam Test

Method C: Standard C-Ring Test

Method D: Standard Double Cantilever Beam Test (DCB)

  Sample Request

Method B:

American Standard (Three-Point Bend) 67.3mm*4.57mm*1.52mm

Chinese Standard (Two-Point Bend) 15-25mm wide, 110-255mm long, specimen of big loading stress (≥ 200MPa), 0。8-1。8mm thick

Method C:

American Standard: outer diameter (OD) ≥15。9mm

Chinese Standard: OD ≥15mm

Specific size refers to the drawings.

Method D:

Chinese and American Standards: 110mm*30mm*10mm

Four-Point Bend:

110-250mm long, 15-50mm wide, and thickness is supplied by client.

  Laboratory

实验室环境

   Service process
Require
───Quick:Customer service reply consultation
 
Apply
───Standard:Fill in the application form, sign the agreement.
 
Testing
───Strictly:Strict compliance with the operating rules for the sample testing
 
Report
───Comply with the reporting procedures and ensure the accuracy of the data.
 
Archive
───Service:Archive customer's samples and contracts

RONDA TESTING——Science, Justice, Innovation, Efficient!
 
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