Wet underwater welding requires considerable skill and, depending on materials and consumables, carries a high risk of fabrication hydrogen cracking. For critical applications, it should only be undertaken by experienced welder divers using established procedures. Also, as there are wide differences in the operability and resulting weld quality obtained with different commercially-available electrodes, the choice of welding consumables should be made with care.
Whilst satisfactory welds can generally be made in the flat position, and, with the better electrodes, in the vertical position, welding overhead presents a considerable challenge, and weld quality in this position is likely to be poorer than in the other welding positions. In spite of this difficulty, it has been recognised for many years that welds of acceptable integrity can be deposited by this process.
Satisfactory repairs have been reported for U.S.A. Navy ships [1-3] and for offshore structures. [1,2] Successful repairs have also been carried out to offshore structures in the Gulf of Mexico, following hurricane damage, [4,5] and in the North Sea.  The integrity and mechanical properties of wet underwater welds have been evaluated by a number of authors e.g. [3,7] , and welds that meet AWS D3.6  class A requirements (that are the same as for welds deposited in air) have been reported [9-11] . Ferritic weld deposits generally show only modest ductility and impact toughness, with Ni-base deposits giving better mechanical properties.
In nuclear applications, satisfactory repairs to stainless steels have been carried out underwater, using stainless steel manual metal arc electrodes. [12,13] However, it should be noted that the welding of ferritic steel with stainless steel electrodes is generally not successful, as fusion boundary cracking, and sometimes solidification cracking, occur. [1,14]
The semi-automatic wet underwater welding processes 'water curtain welding' (with the action of a conical water jet containing a gas shield) and flux-cored wire welding (without a gas shield) have been used with some success. The former is capable of producing high integrity welds. [15,16] Whilst success has been claimed for the latter in the repair of ships  and pipe-lines, [18,19] the quality of welds has generally not reached that achieved with the other welding processes.
- Burner W K: 'Generalised summary of the state of the art of underwater welding' Naval Engineers Journal April 1978 90 68-74.
- Grubbs C E and Seth O W: 'Underwater wet welding with manual arc electrodes' Proc. Int. Conf. on Underwater welding for offshore installations, 1977, The Welding Institute, 1977, 17-33.
- West T C, Mitchell G and Lindberg E: 'Wet welding electrode evaluation for ship repair' Weld J. 1988 69(8) 46-56.
- Cayll D R and Marino J A: 'Inspection assessment and repair of damaged offshore platforms' Proc. Int. workshop on Underwater welding of marine structures, 7-9 December 1994, New Orleans, U.S.A., S Liu, D L Olson, C Smith and J S Spencer, Eds, American Bureau of Shipping, 1995 247-277.
- Maghes A J, Reynolds T J and Smith R L: 'Hurricane Andrew damaged platform repair by wet welding', Ibid 279-293.
- Ibarra S, Reed R L, Smith J K, Pachniuk I and Grubbs C E: 'Underwater wet weld repair of an offshore platform in the North Sea' Proc. First Int. Offshore and Polar Engineering Conf., Edinburgh, U.K., 11-16 August 1991, C P Ellinas, R S Puthli, Y Ueda and S Berg Eds. International Society of Offshore and Polar Engineers, 191, Vol. 4 339-346, and 'The structural repair of a North Sea platform using wet welding techniques' Proc. 23 rd Annual Offshore technology Conf. 1991 Vol. 3 Paper OTC 6652, p 57-66.
- Cochrane D J and Swetnam D: 'Wet welding - a viable technique?' Met. Con. 1986 18(11) 680-685.
- AWS D3.6M: 2010: 'Specification for underwater welding', American Welding Society, Miami, USA 2010.
- Grubbs C E and Reynolds T J: 'Underwater welding: seeking high quality at greater depths', Welding J. 1998, 77(9) 35-39.
- Pett, M 'Wet welding - significant advances in quality': Welding and Metal Fabrication, 2000 68 (4) 22-24.
- Johnsen M R : 'Keeping shipshape through underwater welding', Welding J, 2001, 79 (11) 54-57.
- O'Sullivan J E: 'Wet underwater weld repair of Susquehana unit 1 steam dryer' Weld J. 1988 67(6) 19-23.
- O'Sullivan J E: 'Underwater welding in nuclear applications' in Proc. Conf. on Maintenance and repair welding in power plants, Orlando, U.S.A. 9-11 December 1992, AWS and EPRI 75-83.
- Gooch T G: 'Properties of underwater welds' Met. Con. 1983, 'Part 1 Procedural trials' 15(3) 164-167; 'Part 2 Mechanical properties' 15(4) 206-215.
- Hoffmeister H, Küster K and Schafstall H-G: 'Weld joint properties of medium strength steels after underwater wet MIG-welding by the water curtain process' Proc. Second Int. Conf. on Offshore welded structures, 16-18 November 1982, London, The Welding Institute, 1983, p17-1 - p17-8.
- Irie, T; Ono, Y; Sato, M; Kitamura, N; Ogawa, Y: 'Underwater butt welding down to 10m', Proc. 17th Int. Offshore Mechanics and Arctic Engineering Conf. (OMAE 1998), 5-9 July 1998, Lisbon, Portugal, Ed: C.Guedes-Soares, ASME International, New York, USA, 1998.
- Kononenko V Ya, Gritsai P M and Semenkin V I: 'Using wet mechanised welding in repairing ships hulls in the sea' The Paton Welding Journal 1994 6(12) 498-501.
- Kononenko V Ya and Rybchenkov: 'Experience with wet mechanised welding with self-shielding flux-cored wires in underwater repair of gas and oil pipelines', Ibid. 1994 6(9-10) 401-404.
- Kononenko V Ya and Savich I M: 'Wet mechanised welding using self-shielded flux-cored wires in underwater pipelines repair' Proc. 2 nd Int. Pipeline Technology Conf., Ostend, Belgium, September 1995, R. Denys, Ed., Elsevier, 1995, Vol. II 73-78.
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