There have been few systematic studies on the properties of duplex stainless weldments, and so in this study a large number of experimental tests have been carried out on different wrought and cast duplex stainless weldments (SAF-2205 UNS-S31808) and (Ferralium-225) which are characterized by low carbon content and good balance of ferrite and austenite phases (im 50/50). These experiments have sought to assess the following parameters: - The influence of heat input on microstructure, mechanical and corrosion properties. - The effect of ageing on the microstructure and transformation behaviour. - The effect of consumable composition and type on the microstructure, mechanical and corrosion properties. - The effect of gas back purging on phase balance and corrosion resistance. - The influence of multi-run heating on subsequent properties. The current studies have revealed a number of significant conclusions, such as:- - Heat input has a very small influence on mechanical properties. - Toughness values are increased as the heat input is increased because there is an increased austenite level. - The toughness decreased with decreasing testing temperature. - Ageing for long term at 500°-700° and 800°C has significant effects on hardness, mechanical properties and microstructure. Moreover there is evidence of intermetallic formation. - The microstructure was found to be influenced by the welding process, heat input, composition of filler metal and number of weld passes. - The microstructure examination has indicated that high input rates generally promote austenite formation, due to slower post weld cooling. - The welds have an increased ferrite content compared with the parent metal. - There is a significant increase of ferrite in the HAZ, and as a result the HAZ has a low resistance corrosion. - The austenite/ferrite phase balance in the microstructure has a significant influence on the corrosion resistance. - The change in heat input does not appear to have a direct effect on corrosion, but its effect is secondary through its influence on austenite formation. - The minimum austenite level for good pitting corrosion resistance appears to be greater than 32-35%. - The influence of grain growth is found to be important in controlling corrosion, with high heat inputs favouring grain growth. - The cast materials generally behave in an inferior manner compared to the wrought materials. A generalised model for pitting corrosion in these materials is also presented.