Aluminium shortage 2026: Japan carmakers cut output

Disrupted Gulf shipping puts Japan’s auto supply chain under strain

Japan’s dependence on the Middle East for aluminium has become a near-term operational risk after the Iran conflict disrupted key shipping routes, including the Strait of Hormuz. Companies across autos and components are cutting back production and searching for alternative supply sources as deliveries slow or stop. The exposure is high because aluminium sits in critical parts and assemblies, and many manufacturers typically hold only about two months of inventory. Analysts and industry bodies cited in the reports warn that even if hostilities ease, a return to normal shipping could take months. The situation has started to show up in production plans and output decisions at suppliers and automakers.

Why aluminium is a hard-to-replace input for automakers

Aluminium is the most commonly used metal after steel, and it is valued for being lighter and better at dissipating heat. In vehicles, it is used in engine parts such as pistons and cylinder heads, and also in body panels and alloy wheels. Beyond autos, it is used in electronics, building materials, and packaging such as beverage cans and chip bags. That breadth of use makes sudden supply shocks difficult to absorb, especially when specific alloy grades or block products are required for automotive applications. Industry sources highlighted the risk of shortages in specialised products that can force temporary shutdowns if components cannot be substituted quickly.

What changed after late-February hostilities

The reports said aluminium prices jumped about 13% since hostilities started in late February, reflecting tighter supply expectations and logistics disruption. Shipping through the Strait of Hormuz fell as the conflict escalated, and deliveries from the Middle East to Japanese buyers were interrupted. Refineries in Abu Dhabi and Bahrain were damaged in the early stages of the conflict after Iran attacked regional neighbours in response to the US and Israeli assault, adding a production-side hit to the logistics shock. Even if a peace deal reopens the Strait of Hormuz, shipping could still take months to return to normal levels, according to the reports.

Japan’s exposure: heavy reliance on the Middle East

Japan’s auto industry is among the most exposed. Domestic carmakers source about 70% of their aluminium imports from the Middle East, according to the nation’s top auto lobby. Japan imported around 590,000 tonnes of aluminium from the Middle East in 2025, which the Japan Aluminium Association said was about 30% of Japan’s total aluminium supply. S&P Global analyst Masatoshi Nishimoto described Japan as the most vulnerable country to aluminium shortages, with South-east Asia, China and South Korea also facing “the greatest risk.” In contrast, Bloomberg Intelligence said US companies are not in danger of running out because the US sources most aluminium domestically and from Canada.

Early operational impacts: suppliers and automakers adjust output

Toyota Motor and parts makers such as Denso were cited among the most exposed. Denso and its affiliates reduced monthly output by around 20,000 units, the company said in late March, and reported sizeable losses. Small and mid-sized suppliers are also tightening spending and preparing for tighter conditions. Daiki Kato, CEO of Kato Light Metal Industry, said in late March it was “almost certain” the company would soon have trouble making automobile parts, adding that it would spend more selectively and conserve energy.

Case study: Kato Light Metal’s inventory window and sourcing shift

Kato Light Metal Industry, based in Aichi Prefecture, makes aluminium products mainly for construction and automobiles. It imports about 400 tonnes of aluminium per month, roughly 200 tonnes each from Dubai and Australia. The company said deliveries from the Middle East have stopped, but it has enough inventory to last through May. Beyond that, it plans to buy aluminium from a supplier in South-east Asia. The company’s situation reflects a wider pattern described by the Japan Aluminium Association: manufacturers are seeking alternatives as inventories begin to run dry.

A parallel constraint: naphtha and petrochemical inputs

Separate reporting said the Middle East conflict is also tightening supplies of naphtha and other petroleum products, which are important inputs for chemicals used in auto parts. Kpler data showed Japan’s imports of petroleum products, including naphtha, fell around 30% in March from the previous month. Tighter naphtha supplies were linked to shortages of raw materials for producing plastic components such as ethylene, while prices of butadiene and synthetic rubber used in tire manufacturing were reported to have surged. Tang Jin, a senior researcher at Mizuho Bank, said prolonged tensions were having a direct and profound impact by raising production costs and squeezing automakers’ margins.

Market impact and cost pressure

For automakers, the disruption hits both the cost base and physical availability of raw materials and components. Aluminium prices rising, combined with shipping delays, increases working capital needs and complicates production schedules, especially when inventory buffers are only about two months. The reports noted that hundreds of ships were stuck in the Persian Gulf, creating a bottleneck even if the conflict ends. Some manufacturers rerouted shipments from the Strait of Hormuz to the Cape of Good Hope in South Africa, which was reported to nearly double delivery times to about 100 days. For investors tracking global auto and metals supply chains, the key signals are production cuts, inventory duration, and how quickly alternative suppliers can be qualified under strict specifications.

Key figures and operational details

Analysis: why this shortage risk is structurally difficult to fix quickly

The reports suggest the disruption is not limited to one chokepoint. It combines constrained shipping through the Strait of Hormuz, damage to refineries in Abu Dhabi and Bahrain, and a slow recovery path for production and logistics. A major Middle East producer predicted it would take at least a year to restore full production, while JPMorgan Chase analysts said the industry had entered a “black hole” it will not easily come back from. Even where alternative sourcing is possible, qualifying new suppliers for automotive-grade alloys can be slow due to strict specifications, raising the risk of temporary stoppages in specific components. The knock-on effects extend beyond metals into petrochemical feedstocks such as naphtha, affecting plastics and tires.

Conclusion: production adjustments now, longer recovery later

Japan’s auto industry is already reacting through output cuts, logistics adjustments and alternative sourcing plans as aluminium and related inputs become harder to secure. With inventories often sized for roughly two months, the reports indicated disruptions could start appearing broadly by late April or early May. Automakers including Toyota and Nissan said they are monitoring the situation and taking appropriate measures, while some manufacturers have halted or reduced production of Middle East-bound models due to shipping disruption. The next milestones will be any reopening of shipping lanes, the pace at which damaged production facilities in the Gulf return online, and whether shipping congestion in the Persian Gulf clears.