Under the terms of the agreement 200 tonnes per annum of NdPr metal will be shipped in 2026 followed by 360tpa in 2027.
Between 2028-2030 there will be 400tpa sent as operations at Nolans ramp up.
There is an option to extend the agreement for two years.
This deal means Arafura has contracts over about 53% of the targeted 85% of production earmarked for export.
First production is scheduled in 2025.
Siemens Gamesa has a production facility in Cuxhaven, in Germany's Lower Saxony region where it makes and assembles all components for the hub, generator and backend into the turbine.
Arafura managing director Gavin Lockyer said the company was pleased to have concluded negotiations on the second offtake agreement.
"Siemens Gamesa is the world's leading manufacturer of offshore wind turbines and this agreement complements our strategy to create supply diversification into the renewable and e-mobility sectors," he said.