The degree of corrosion of weldments on offshore structures and vessels depends upon the metallurgical characteristics of steels and welding consumables, the welding procedures, and the environmental severity. A new procedure has been developed for evaluating the preferential corrosion susceptibility of weldments at the heat affected zone (HAZ) and in the weld metal. The procedure uses short term laboratory tests to determine the corrosion susceptibility of the HAZ and weld metal for an "as-welded" specimen. These tests primarily involve the use of the Scanning Reference Electrode Technique (SRET), a highly sensitive technique with good resolution, requiring only a few days to clearly delineate the preferential corrosion susceptibility of a weldment. An empirical design method is also presented which determines, without laboratory testing, the preferential corrosion susceptibility of some weldments with heat inputs ranging from 1.1 to 4.2 kJ/mm. The use of both the SRET apparatus and the design method allows for the selection of materials and welding procedures to obtain maximum resistance to preferential weld zone corrosion.

The accuracy of the SRET apparatus was benchmarked against a collection of long term field tests, using coupon weldments attached to offshore structures and vessels, as well as field corrosion data gathered from actual ship hull weldments. A good correlation was found between the SRET tests and the field data. Also, the design method was derived from the same data base of test data.

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