Three of the world's largest aluminum producers -- Aluminum Co. of America, Alcan Aluminium Ltd. and Kaiser Aluminum & Chemical Corp. -- yesterday reported net losses for 1985. World aluminum prices remained relatively low during 1985 because of abundant supplies of the metal.

Pittsburgh-based Alcoa, the world's largest, said it lost $16.6 million during 1985, largely because of special charges stemming from plant closings. The company had net earnings of $256 million ($3.13 a share) in 1984. Alcoa said it had a $121 million loss in its fourth quarter compared with a $14.7 million loss in the same period a year earlier.

Sales in the fourth quarter fell to $1.21 billion from $1.39 billion a year earlier, while sales for all of 1985 dropped to $5.16 billion, from a record $5.75 billion in 1984.

Alcan, the Montreal-based company that is the world's biggest marketer of primary aluminum, lost $180 million (U.S.) during 1985 compared with a profit of $253 million ($2.17) in 1984. The company cited $252 million in after-tax charges for the full-year loss.

Alcan said it had a fourth-quarter loss of $212 million compared with a profit of $20 million (20 cents) in the same period of 1984, because of a special $215 million after-tax charge.

Sales during the fourth quarter totaled $1.41 billion compared with $1.23 billion a year earlier. For the entire year, sales totaled $5.51 billion, compared with $5.27 billion in 1984.

Kaiser Aluminum, the third-largest aluminum producer in the United States, reported a loss of $186.5 million for 1985, including asset write-downs and other charges, compared with a $97.4 million loss in 1984. Kaiser, which is the target of a takeover attempt by a group led by Oklahoma investor Joseph A. Frates, posted a fourth-quarter loss of $107.8 million compared with a profit of $3.9 million (7 cents) in the same period of 1984. The quarterly loss included an after-tax charge of $119.2 million in asset write-downs.

Sales for the quarter increased to $512.5 million from $520.8 million a year earlier, while 1985 sales fell to $2.03 billion from $2.12 billion in 1984.

*Penn Central Corp. reported sharply lower 1985 net income of $110.8 million ($2.76 a share), as record profits in telecommunications and energy were offset by losses in electronics and marine construction. Net income for 1984 was $170 million ($3.82). Net sales were $2.5 billion compared with $2.6 million in 1984.

Net income for the 1985 fourth quarter was $27.2 million (68 cents) compared with $39 million (97 cents) in the 1984 fourth quarter. Net sales were $666.6 million compared with $710.5 million in the 1984 fourth quarter.

*United Technologies Corp., a giant aviation conglomerate and the nation's seventh-largest manufacturing company, said that it earned nearly $30 million more in 1985 than the previous year, despite a drop in orders for spare parts and jet engines.

Net income from continuing operations rose to $636.4 million ($4.76 a share) for the year from $608.9 million ($4.97) in 1984 as sales totaled $15 billion in 1985 compared with $14.8 billion in 1984. Fourth-quarter income from continuing operations was $165.9 million ($1.25), a 4 percent gain over $160.1 million ($1.21) a year earlier. Fourth-quarter sales from continuing operations totaled $4.2 billion, up from $4 billion in the 1984 fourth quarter.