Two cheers for "Art Inc.: American Paintings from Corporate Collections," which goes on view today at the Corcoran Gallery of Art.

One slightly tired cheer for its handsome pictures: its Homers, Hoppers, Warhols and Wyeths. They often please; they rarely shock. This exhibition offers, as have countless shows before it, yet another survey of the standard repertory of accepted U.S. art.

What makes "Art Inc." special is not its pictures but its patrons. All the works on view were purchased by big businesses: IBM, Playboy, U.S. Steel, Westinghouse, fast-food sellers, cotton brokers, insurance companies and banks. One cheer for these 30 corporations which - unlike almost all the others - have dared to spend a tiny fraction of their monies on handmade works of art.

The third cheer, however, will to be postponed until corporate art buying becomes something more than tokenism.

In 1978, General Motors, one corporation among thousands, spent $240 million on its incessant ads. In 1976, according to an estimate cited in the catalog, all American corporations together spent the "rather small amount" of "almost $4.5 million" on "expenditures for art."

That figure may be underestimation, but it is still modest compared to the outlay for onyx ashtrays, teak desks, potted plants, custom-designed wastebaskets and other office decorations.

"The actual expenditures for art by corporations," the catalog observes, "may have declined in the past six years." Corporate comptrollers are not yet modern medicis. This exhibition does notindicate a trend.

The first corporate collections were formed for advertising purposes. In the early years of this country, the Atchison, Topeka and Santa Fe railway traded train rides for works of Western art. "The Santa Fe," writes Mitchell Douglas Kahan in the catalog, "Provided free transportation to the southwest in return for paintings, which were reproduced in magazine advertisements and on the menus used in dining cars. In this novel manner, the company not only acquired a fascinating collective portrait of the southwest but also stimulated the art colony in New Mexico."

The paintings that Steinway & Sons began to commission during World War I also work as ads. Three are in this show. One, by N.C. Wyeth called "Beethoven and Nature," shows us the composer pondering a stream. A second shows the founder of the piano firm busy at his workbench. Here the advertising content is unambiguous. But when Playboy buys a giant lipstick mouth painted by Tom Wesselmann is supporting modern art or purchasing an ad?

Seven of the corporations represented are banks. "The reasons are several," writes Kahan. "Banks have more usable space visible to the public than other kinds of businesses.Their spaces are designed for public reception and are unencumbered by merchandise; they virtually demand art." Banks, which used to show us marble pediments and columns, those signs of cultivated permanence, today prefer displaying costly works of art.

The First National Bank of Chicago, for instance, owns 2,600 works of art selected by Katharine Kuh. The oldest dates from the 6th century B.C.; its most recent works are new.

Although the bank has purchased works by Gilbert Stuart, Frederick Remington and Rodin, the three lent to this show are not by big names. One is a lovely silvery seascape by Alfred Thompson Bricher; the second is a modest still life of green grapes painted in 1881 by Andrew John Henry Way; the third, and operatic view of the Grand Canyon, was painted in 1886 by one C.H. Chapin about whom almost nothing is known.

Three other 19th-century landscapes, by David Johnson, Worthington Whittredge and Albert Bierstadt, classy pictures all, represent the Cleveland Trust Co. Works by Edwin Dickinson, Fairfield Porter and Arthur Dove are here from the Commerce Bank of Kansas City; Chase Manhattan, Citibank, and Seattle-First National are here too.

One expects big banks to recognize investments. When Seattle-First National bought its Morris Louis, when Chase Manhattan shelled out for its splendid Burchfield, and when Citibank acquired its early Richard Estes, they were not only enhancing their corporate reputations. They were also buying inflation-proof objects that might easily, at any time, be turned into cash.

Of the modern painters in this show - Roy Lichtenstein, Ellsworth Kelly, Josef Albers, Richard Diebenkorn, Saul Steinberg, Helen Frankenthaler, Romare Bearden, et al - many are among the bluest of blue chips. "It is interesting to note," says Kahan, "that works by famous artists are sometimes sold by companies when they become extraordinarily valuable, not primarily for their cash value, but because they pose security problems."

Though IBM, the first American "corporation to assemble a group of artworks solely for the purpose of forming a collection and not for the illustration of advertisements," has been buying paintings since 1939, most of the collections represented here were formed in the '60s. A number of walls of the shiny corporate headquarters that went up in that decade.

In America today, the supply of paintings far exceeds the demand. Artists have to scuffle to store the countless paintings, prints and drawings that they cannot sell. Meanwhile, on K Street, workers by the thousands sit at costly desks filling costly ashtrays and staring at blank walls.

Big business has many reasons to buy art. It decorates the work space, cuts through tedium, is good for public relations, cheers up employes and may prove a fine investment as well. There is, so we are told, an art boom in America. But for the most part, corporations have yet to catch on.

Edward W. Duffy & Co. is a notable exception. The firm makes industrial steam valves, pipes and fittings, and has been hiring local artists to decorate its warehouse in Detroit. Some of their work is on display here.

"Art Inc." was organized by the Montgomery, Ala., Museum of Fine Arts. Washington's Walter Hopps served Henry Flood Robert Jr., that museum's director, as curatorial adviser. Former postmaster general Winton M. Blount, who raised money for the show from many Alabama corporations, his own included, and who also lent his firm's Edward Hopper and its Stuart Davis, is the chief sponsor of the exhibition. It will travel to Indianapolis and to San Diego, and perhaps to Europe, after closing here on July 14. CAPTION: Picture, Roy Lichtenstein's "Cubist Still Life," a detail.