HELM joins Redox, Migao, Mitsui as customers for product from APC's Lake Wells project in Western Australia, where operations are due to ramp up to steady state output in 2023.
APC is aiming to finalise debt facilities and regulatory approvals this quarter.
APC needs about A$208 million to build Lake Wells, with the debt/equity mix expected to be about 65:35.
The project has a net present value of $441 million.
Earlier this month APC raised $7 million by issuing new shares priced at 11c each.
Shares in APC were up 4% to 13.5c in afternoon trade, capitalising the company at $74 million.
The stock was trading at levels around 5c mid-year.