AS 4036-1992

1 - AS 4036:1992 CORROSION OF METALS - DISSIMILAR METALS IN CONTACT IN SEAWATER
4 - PREFACE
5 - CONTENTS
6 - FOREWORD
7 - SECTION 1 - SCOPE AND GENERAL
7 - 1.1 SCOPE
7 - 1.2 REFERENCED DOCUMENTS
7 - 1.3 DEFINITIONS
8 - SECTION 2 - FACTORS INFLUENCING GALVANIC CORROSION
8 - 2.1 SCOPE OF SECTION
8 - 2.2 POTENTIAL DIFFERENCE BETWEEN DISSIMILAR METALS
8 - 2.3 NATURE OF THE ELECTROLYTE
9 - 2.4 CATHODE/ANODE AREA RELATIONSHIP
9 - 2.5 METALLURGICAL CONDITION OF THE METAL
9 - 2.6 DEFECTS IN METALLIC COATINGS
9 - 2.6.1 General
9 - 2.6.2 Cathodic coatings
9 - 2.6.3 Anodic coatings
10 - 2.7 NOBLE (CATHODIC) METAL ION CONTAMINATION
10 - 2.8 CARBONACEOUS MATERIALS
10 - 2.9 MOVEMENT OF ELECTROLYTE
10 - 2.10 FORMATION OF SURFACE FILMS (CORROSION PRODUCTS)
10 - 2.11 POLARITY REVERSAL
10 - 2.12 TEMPERATURE
11 - SECTION 3 - CONTROL OF GALVANIC CORROSION
11 - 3.1 SCOPE OF SECTION
11 - 3.2 FEATURES OF DESIGN
11 - 3.3 INSULATION
11 - 3.4 CATHODIC PROTECTION
11 - 3.5 COATINGS
11 - 3.5.1 Metallic coatings
11 - 3.5.2 Non-metallic coatings
12 - 3.6 PASSIVATION OF THE METAL SURFACE
12 - 3.7 JOINTING AND SEALING COMPOUNDS
12 - 3.8 INHIBITORS
13 - SECTION 4 - COMPATIBILITY OF DISSIMILAR METALS IN CONTACT
13 - 4.1 SCOPE OF SECTION
13 - 4.2 CODE FOR RATING DISSIMILAR METALS
13 - 4.3 CORROSION RESISTANCE OF DISSIMILAR METALS IN CONTACT WHEN IMMERSED IN SEAWATER
15 - APPENDIX A - TEST METHOD FOR THE DETERMINATION OF ELECTROCHEMICAL CORROSION RATINGS FOR PAIRS OF DISSIMILAR METALS IMMERSED..
15 - A1 SCOPE
15 - A2 PRINCIPLE
15 - A3 APPARATUS
15 - A3.1 Zero resistance ammeter (ZRA)
15 - A3.2 High impedance voltmeter
15 - A3.3 Test cell holder
15 - A3.4 Reference electrode
15 - A3.5 Glassware
15 - A4 REAGENTS
15 - A4.1 General
15 - A4.2 Sodium chloride
15 - A4.3 Sodium sulfate (anhydrous)
15 - A4.4 Stock Solution No. 1
15 - A4.5 Stock Solution No. 2
18 - A4.6 Sodium hydroxide solution
18 - A5 PREPARATION OF ARTIFICIAL SEAWATER
18 - A6 SAMPLE PREPARATION - TYPE 1 (CYLINDRICAL)
18 - A6.1 General
18 - A6.2 Sample size
18 - A6.3 Machining the sample
18 - A6.4 Electrical connection
18 - A6.5 Sample mount
18 - A6.6 Sample assembly
19 - A6.7 Grinding and polishing
20 - A7 SAMPLE PREPARATION - TYPE 2 (SHEET)
20 - A7.1 General
20 - A7.2 Electrical connection
21 - A7.3 Sealing
21 - A7.4 Sample assembly
21 - A8 PREPARATION FOR TEST
22 - A9 TEST PROCEDURE
22 - A9.1 General
22 - A9.2 Procedure
22 - A10 METHOD OF DETERMINATION OF CODE FOR THE RATING OF TEST RESULTS
24 - A11 TEST REPORT
24 - A12 SIGNIFICANCE OF TEST RESULTS
25 - APPENDIX B - BASIC THEORY OF GALVANIC CORROSION
25 - B1 SCOPE OF SECTION
25 - B2 CORROSION PROCESS
25 - B3 CORROSION CELLS
26 - B4 GALVANIC SERIES FOR METALS AND ALLOYS IMMERSED IN SEAWATER BASED ON CORROSION POTENTIAL MEASUREMENTS

Presents a method for testing dissimilar metal couples immersed under standard conditions in seawater and for the determination of ratings for the additional corrosion which may occur on the more anodic metal of each couple. In addition, ratings are given for 245 commercially-significant dissimilar metal couples.

This Standard provides a test method to determine the degree of additional corrosion of the more anodic of two metals in direct electrical contact, when immersed under standard conditions in stagnant artificial seawater.The test method given in Appendix A requires the measurement of the galvanic current over a period of 28 days, and rates the amount of additional corrosion of the metal under consideration into four categories.The Standard provides a table (Table 4.1) which gives such ratings for a variety of commercially-significant dissimilar metal couples (including alloys and carbon). This table can be used to give a qualitative assessment of the performance of dissimilar metal couples when they are immersed in actual seawater.The Standard also provides information on factors influencing galvanic corrosion and in addition, provides guidelines on controlling this corrosion.NOTES:1 The factors controlling galvanic corrosion given in Section 3 should be taken into account when evaluating the test results in terms of expected performance in actual seawater conditions and may reduce the viability of some galvanic couple ratings given in Table 4.1.2 The basic theory of the galvanic corrosion of dissimilar metals is given in Appendix B.

First published as AS 4036-1992.