The Chinese distribution company Sinofert Holdings is described as the country's leading fertiliser supplier and distributor.
Salt Lake said it soon plans to start construction of a demonstration plant at Lake Way producing up to 50,000tpa of high quality SOP, with it planning to distribute production through a "small number of global distribution partnerships".
Salt Lake already has an offtake MoU with Mitsubishi.
Lake Way could cost about $50 million to bring into production, with initial output flagged for early 2020.
Lake Way is a previously mined gold open cut near Wiluna containing "super saturated brine".
Salt Lake started the September quarter with A$5.7 million cash.
The company features well recognised corporate executive Ian Middlemas and his team of Matthew Syme and Mark Pearce, and well-known capital markets operative Jo Battershill.
Shares in Salt Lake were up 3.3% to 46.5c in morning trade, capitalising the company at $81 million.