Ad agencies feast on boom in corporate imagemaking

''Gee. . . . No, GTE.'' ''Alcoa can't wait.'' ''A company called TRW.''

For GTE, Alcoa, and TRW, these ad slogans are expected to do more than provide a catchy jingle. They are the key to selling the company's image at least as much as its products.

Advertising the corporate image, big business has found, helps sell everything from shares of stock in the corporation to business equipment, airline travel, and automobiles. Although image advertising is estimated to have accounted for less than 5 percent of US ad dollars spent last year, that still adds up to a respectable $2-to-$2.5 billion in corporate and business-to-business advertising.

And, over the past few years, this specialized form of advertising has been one of the fastest-growing areas in the business. With increasing numbers of companies using it, and more and more going into the highly visible and expensive TV medium, such image, or ''corporate,'' advertising is expected to increase overall billings this year by a hefty 15 to 20 percent - or nearly three times expected media increases.

Companies such as Alcoa, Campbell Soup, Continental Insurance, Exxon, Ford, and Pan Am are using corporate advertising to:

* Boost the value of their stock in the public mind.

* Increase public awareness of the company and what it has to offer.

* Attract high-caliber recruits.

* Sell the company's point of view in what is now being called issue, or advocacy, advertising.

Recently, British Airways announced a substantial increase in its advertising budget - both in the United States and abroad - for a corporate ad campaign designed to turn the government-owned airline into a private corporation.

One of the hottest growth areas for corporate advertising is ''market-prep advertising,'' according to Thomas F. Garbett, vice-president of Doyle, Dane, Bernbach and author of ''Corporate Advertising - The What, the Why, and the How.''

''Our corporate clients, such as GTE and IBM, are using more and more market-prep advertising for establishing an image of themselves, for positioning products and preselling them, and for preparing the marketplace for the acceptance of new product lines,'' he says. ''Corporate advertising, which represents about 10 percent of our domestic billings, is one of the single fastest-growing segments in the agency, thanks in large part to the current interest in market-prep advertising.''

To serve their growing lists of corporate clients, many of the big Madison Avenue agencies are forming separate units such as J. Walter Thompson's Brouillard Communications and Foote, Cone & Belding's FCB Corporate. Ogilvy & Mather is about to announce its own special group to handle corporate advertising clients.

''More and more CEOs [chief executive officers] are becoming increasingly comfortable with the concept of using corporate advertising along with their public-relations programs to enhance the price of their company's stock, as well as improve the perceived value of their product lines in the eyes of their customers,'' says Bruce N. Jackson, executive vice-president and general manager of Needham, Harper & Steers's Issues and Images in New York. Issues and Images, which does advertising and public relations for government agencies as well as for corporations, created the much-talked-about ''Say yes to Michigan'' campaign , and was recently awarded the account to promote Israeli tourism.

Corporate advertising clients tend to stay with the same agency longer than some of the more volatile product advertisers - another reason why these accounts are so highly prized by many agencies. ''Continuity is very important in corporate advertising - not just in terms of a specific corporate campaign, but also in terms of the agency staff serving a particular client,'' according to Donald C. Porteous, executive vice-president of the corporate-communications division of Creamer Inc.

Creamer, which boasts a client-longevity record of more than twice the industry average, has nearly $40 million of its $200 million in billings in corporate advertising, with perhaps another $25 million assigned to business-to-business advertising. For Alcoa, a client of 30 years standing, Creamer created the TV campaign, ''Alcoa can't wait.'' Recently Creamer and its client Raytheon celebrated a decade of doing business together by displaying a 10-year period of print ads, all from the same corporate-advertising campaign.

''Our corporate-advertising objective is to build awareness of Raytheon within the financial and business community as a successful, growing, and highly diversified company,'' commented Van M. Stevens Jr., director of advertising at Raytheon, which is based in Lexington, Mass. ''The advertising created by Creamer for us has been immensely helpful in positioning our company as an attractive investment opportunity for the financial community and a good company for our customers to do business with.

''Based on our past success in meeting our corporate advertising objectives with this campaign, we expect our expenditures on it to continue to grow this year to the $3-to-$4 million range.''