Underwater welding offers a mode of assembly or repairs the structures underwater. It is a type of technology for repairing marine structures. Unconventional methods such as clamp and grout repairs (which may set up inappropriately high loading on offshore structures), and the use of bolted flanges for the tie-ins, are not necessarily always satisfactory.
CO2 sand casting or Hobby Aluminum casting is suitable for urgent and heavy orders with high accuracy and good surface finish on castings required. Hobby mould casters used this method because in this method elimination of core drying machine, but it is not an economical process. The only expense hobby mould caster encounters are the cost of the CO2 cylinder, regulator, and hoses and hand held applicator gun or nozzle. The operation is fast and the possibility of rejections is less. CO2 is a sand molding technique and it uses grain sand which is mixed with a solution of sodium silicate that acts as binding agent. CO2 gas is used to harden the mass of sand after the mould has been made.