If a Canadian consumer purchases an American automobile, the car comes with at least a three-year warranty against rust and corrosion.

But if an American consumer buys the same car in the United States, there is no such protection. A consumer group here wants to change that.

The Center for Auto Safety, a Washington-based consumer organization has written the chairman of the four major U.S. car manufacturers calling for the automakers to provide voluntary domestic guarantees against rust "to prevent more federal regulation."

"American motorists will be exposed to hazards [this winter] of automotive rust that costs them up to $14 billion annually," wrote center director Clarence Ditlow citing National Bureau of Standards figures. "During the past few years the number of consumers who complain to the center concerning corrosion of their automobiles has dramatically increased."

Ditlow said that in 1975 the Automobile Protection Association of Canada and the Center for Auto Safety revealed jointly that Ford Motor Co. had begun a secret adjustment policy to cover premature rusting on some vehicles and that the disclosure led to the development of Canada's voluntary anticorrosion code of 1978.

Now, Canadian owners of 1978 and later model vehicles have at least a three-year or 74,000 mile (120.000 kilometer) warranty against perforations; there will be a five-year of 124,000 mile (200.000 km) warranty for 1981 and later models.

Canadian car owners also have one-year 24,000 mile warranties against surface corrosion.

"Cars sold in the United States are identical to those sold in Canada." Ditlow wrote, "However, the auto companies have discriminated against American consumers by not giving the equal rust protection rights."

"At a time when [domestic automakers] are crying out against federal regulation." Ditlow added the "refusal to voluntarily give American consumers the same warranty against rust that Canadian consumers get is such an anticonsumer action that it demands federal regulation."

In a recent interview in the publication Automotive News W. Warren Allmand, Canadian minister of consumer and corporate affairs called the Canadian voluntary warranty a "unique" way of working to make automakers responsive to consumers needs and a far better way to go than the U.S. route of regulation.

"In recent years." Allmand said, "there has been a growing appreciation in Canada that it is not appropriate for every problem that arises in the marketplace to be resolved through the formal and legislative powers of the government.

"Rather we believe that a more effective operation of the marketplace can be achieved if there is a minimum of legislation imposed on buyer and seller with industry and consumers showing a greater sense of responsibility."

Allmand said however that he was monitoring industry's performance on the rust warranties and if it does not meet promised standards he will not hesitate to recommend legislation.