Directors of Maryland National Corp., parent company of Maryland National Bank, have elected Alan P. Hoblitzell Jr. chairman. He succeeds Robert D. H. Harvey, who will become vice chairman before retiring in August. Hoblitzell, 53, was named president of the Baltimore bank holding company in 1976 and chief executive in 1983. The bank said he will retain those titles.

American Express Co. has promoted Harry L. Freeman, formerly senior vice president of the financial and travel-related services company, to executive vice president for corporate affairs and communications, and Howard A. Menell, previously director of government affairs, to vice president for government affairs. Freeman, who commutes to the company's New York headquarters from his home in Chevy Chase, will have responsibility for government relations, international trade relations and consumer affairs. He was director of the Agency for International Development during the Nixon and Ford administrations. Menell worked for the Senate Committee on Banking, Housing and Urban Affairs, and was staff director and counsel to the Senate securities subcommittee.

Riggs National Bank has appointed Executive Vice President George P. Clancy, 41, to a new assignment in the office of Chairman Joseph L. Allbritton, where he will oversee special projects involving Riggs' long-term development. Clancy, recently returned to Washington after serving as general manager of the bank's London office, also will be Riggs' representative to the board of the AP Bank Ltd. of London, a recently acquired subsidiary. In a separate announcement, Frank L. Cerutti, 36, a former vice president with InterFirst Bank Dallas, has been named senior vice president for corporate banking.

Former Massachusetts senator Edward W. Brooke has been named chairman of the board of The Boston Bank of Commerce, New England's only minority-owned and operated commercial bank. Brooke, now a partner in the Washington law firm of O'Connor & Hannan, was the first black elected to the Senate since Reconstruction. He served from 1967 to 1979.

Washington Mutual Investors Fund has appointed three new members to its advisory board. They are Daniel J. Callahan III, president of American Security Bank; Robert W. Dudley, chairman and president of Consumers Gas Utility Co. in Huntington, W. Va., and Vernon W. Holleman Jr., president of Qualified Pension/Profit Sharing Consultants.

Student Loan Marketing Association has announced five appointments: Jay C. Planalp Jr., formerly assistant vice president at GEICO, has been named vice president and internal auditor. Robert D. Friedhoff, previously assistant vice president for corporate accounting, has been promoted to vice president and controller. Robert S. Inglis, formerly assistant vice president for contract servicing, has been promoted to vice president for contract servicing. Edward C. Campbell, formerly director of office and support services, has been appointed assistant vice president for administrative services. And D. Kaye Arnold, formerly director of financial planning and analysis, has been named assistant vice president.