China shipped 31,666 metric tons of sulfuric acid to Chile in September, its first deliveries there since May. Chinese customs figures compiled by market data firm IndexBox show Chile took 93.5% of China’s acid exports for the month. The restart matters to American buyers because Chile is where most US refined copper imports come from.

The US Geological Survey (USGS) puts Chile’s share of US refined copper imports at 68% for 2021 through 2024 in its 2026 copper overview. The same report places US net import reliance for refined copper at 57% of apparent consumption in 2025. Acid availability at exposed Chilean processing plants can therefore matter to US buyers through the copper they import, without any direct US purchase of that acid.

Domestic Sulfur Reduces Direct Exposure

The war involving Iran cut into Gulf sulfur shipments this spring, and commodity analytics firm Kpler reported in June that global sulfur exports had fallen 45% below end-February levels. China restricted acid exports to protect its fertilizer supply. Its September total of 33,873 metric tons, in figures from commodity information provider Shanghai Metals Market, remained far below the 116,703 tons shipped in May.

The United States has less direct exposure at the chemical level. Most domestic sulfur is recovered at petroleum refineries, natural gas plants and coking plants, and the USGS sulfur summary estimates net import reliance at just 14% in 2025. Sulfuric acid imports came mainly from Canada and Mexico.

Imported Metal Carries the Exposure

Chile’s vulnerability sits in copper leaching, where operators without their own smelter acid buy it on the seaborne market. Nickel follows a different path. US primary nickel imports come mostly from Canada, Norway, Australia and Brazil according to the USGS, which also puts Indonesian mine output at 2.6 million of 3.9 million tons worldwide in 2025.

Indonesia received no Chinese acid for a fourth straight month, and Kpler estimates its high-pressure acid leach (HPAL) plants draw roughly 75% to 80% of their sulfur from the Middle East Gulf. S&P Global Market Intelligence flagged those HPAL operations as the weak point in a March analysis. S&P’s concern centers on particular processing routes, not a shortage across all nickel products. For US buyers, global nickel markets and battery material chains are a possible channel for any effect, more plausibly than direct shipments. The same indirect pattern drove the sulfur squeeze on phosphate producers earlier this year.

Questions for US Metal Suppliers

Buyers of copper cathode, wire and battery materials can ask where their metal is refined and by which process. Suppliers relying on Chilean leach output or Indonesian HPAL nickel should be able to explain their acid sourcing and any qualified alternatives. Buyers can also separate temporary surcharges from changes in delivery commitments, a lesson reinforced by Gulf port disruptions and the helium shortfall hitting chipmakers.

September’s figures show a partial recovery concentrated in Chile. Later customs releases can show whether shipments broaden to Indonesia and other markets, while official Chinese notices would be needed to confirm any change to the export restrictions.