Dr. B. Floyd Brown, 61, a metallurgical engineer and a senior research scientist in the chemistry department at American University since 1973, collapsed Sunday on the sidewalk on the 4400 block of Martin Luther King Jr. Ave. near his home in southwest Washington.

The D.C. medical examiner said Mr. Brown, who was pronounced dead at the scene, died of a heart-related ailment.

An authority on corrosion-resistant metals, Dr. Brown headed the Naval Research Laboratory's Physical Metallurgy Branch here from 1954-72. During that time, he was responsible for the Navy's Marine Corrosion Research Laboratory at Key West and was scientific officer of a joint research project on stress-corrosion cracking for the Navy, an industrial laboratory and six universities.

His awards include the E.O. Hulburt Science Award, the Naval Research Laboratory's highest scientific award; the Navy Group Achievement Award in Marine Corrosion; the Navy's Distinguished Civilian Service Award; the Sam Tour Award from the American Society for Testing and Materials, the George Kimball Burgess Memorial Award from the Washington Chapter of the American Society for Metals and the William Blum Award from the National Capital Section of the Electrochemical Society.

Dr. Brown was born in Rushtown, Ohio. He graduated with distinction with a degree in metallurgical engineering from the University of Kentucky in 1941 and served in the Navy during World War II.

He earned master's and doctor's degrees from the Carnegie Institute of Technology in 1948 and 1950. Dr. Brown did postdoctoral research at Cambridge University in 1953.

Before joining the Naval Research Laboratory, he was a research associate at the Massachusetts Institute of Technology and a member of the graduate faculty at North Carolina State University, where he organized the metallurgical research laboratory.

He was a consultant for the Central Institute for Industrial Research in Oslo, Norway.

Dr. Brown was a fellow of the American Society for Metals, and was a member of Foundry United Methodist Church in Washington.

Survivors include two brothers, Paul H. Brown of Cary, N.C., and Theodore C. Brown of Raleigh; and a sister, Elma Amos of Catlettsburg, Ky.

The family suggests that expressions of sympathy be in the form of contributions to the American Heart Association or to the Memorial Fund at Foundry United Methodist Church in Washington.