Sibu - As in Sibu in Sarawak?
If so, I don't know what local automotive services you might have available. For slight to moderate surface rusting if you have access to a radiator repair shop some of these radiator shops will clean and seal the inside surface of the tank for you. You can also do this yourself if you are so inclined. Eastwood and POR offer kits for cleaning and sealing gas tanks.
[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://www.eastwood.com/gas-tank-sealer-kits-eastwood-gas-tank-sealer.html
[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://www.por15.com/POR-15-Fuel-Tank-Repair-Kit
There are probably other kits available.
I used the POR 15 kit on a tank about 7 years ago (not my NSX) and that tank remains in good condition. Be aware that the tank sealer material (the final step) is quite thick and when it finally dries it is exceedingly hard. This is a fairly time consuming process and you need to keep rotating the tank while the compound set up to ensure that all the inside surfaces get coated. Once you start the process you can't stop so no running to a store to get something that you forgot that you need. The NSX has vents for the tank and if you get the sealer into the vents and let it harden it will render the tank useless. You need a good sized compressed air supply to blow the vents and lines clear of sealer as the sealer sets up. If the tank is not badly rusted you might be better off to just use the degreaser and metal prep compounds to clean up the tank and skip the sealer process.
As an observation, the NSX has a sealed Evap system with filters. The system admits air to the tank when the engine is running; but, closes off when the engine shuts down so you should not have huge amounts of humid air entering the system and causing corrosion. Did you store the car for a period of time with a close to empty tank? That might have created the conditions for corrosion in the tank. Also, are you using high content ethanol or methanol (I expect forbidden by Honda) blended fuels which can be very reactive?[/FONT][SUB][SUP]<strike>
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