Methods for fastening aluminum deck-house to steel deck
Methods for fastening aluminum deck-house to steel deck
Hello everyone, I am currently working on the 2nd class naval architecture and need some help with a question. what are the methods employed to fasten aluminum to steel and what can be done to mitigate the corrosion problems. I'm not sure but i believe riveting may be used. Any help is aprreciated, thanks......................Sprocket
Hi Sprocket, Reed's volume five (fifth ed) fig 12.7 is the good old fashioned way. Basically a bolt that is completely insulated with various non metallic (Neoprene) materials such as ferrules, gaskets and silicone; this is necessary to prevent galvanic action. The high tech way is with a structural adaptor that has an upper layer of aluminium and a lower layer of steel and the plates are simply welded to the adaptor in the usual way. You can check out this method at www.triclad.com Good luck
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The explosion bond seam must be installed high enough in the structure that SW does not lay against it at deck level. You will get electrolysis and it is expensive to repair. So you would have a section of say 8" of steel deckhouse, then the transition to aluminum.
The riveted seam in fitted in older ships as Sebastien says and is problematic in that the neoprene insolator begins to fail after a number of years leading to leakage and corrosion problems. It is a PITA to renew in failed areas as it has to be wedged apart to allow cropping and welding of the new sections of aluminum and steel in, installation of the new insulator material and then re-rivetting. Of course this is after you strip out all the joiner bulkheads and insulation if whatever space in the accomodations that the seam has failed in. (Praying fervently that you do not discover asbestos) . If you have leakage behind the Joiner bulkheads, it will go under the deck underlay and cause deck and bulkhead corrosion. (Guess what I am repairing ).
The riveted seam in fitted in older ships as Sebastien says and is problematic in that the neoprene insolator begins to fail after a number of years leading to leakage and corrosion problems. It is a PITA to renew in failed areas as it has to be wedged apart to allow cropping and welding of the new sections of aluminum and steel in, installation of the new insulator material and then re-rivetting. Of course this is after you strip out all the joiner bulkheads and insulation if whatever space in the accomodations that the seam has failed in. (Praying fervently that you do not discover asbestos) . If you have leakage behind the Joiner bulkheads, it will go under the deck underlay and cause deck and bulkhead corrosion. (Guess what I am repairing ).