NBS SPECIAL PUBLICATION 479 U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards NATIONAL BUREAU OF STANDARDS The National Bureau of Standards^ was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the Office of Experimental Technology Incentives Program. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essen- i tial services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Center for Radiation Research — Lab- oratory Astrophysics- — Cryogenics^ — Electromagnetics^ — Time and Frequency". | THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measure- | ment, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational insti- j tutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and i distributes materials. standard reference The Institute consists of the Office of Standard Reference Materials, the OflBce of Air ; and Water Measurement, and the following divisions: j Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry. j THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services developing and promoting the use of avail- I able technology; cooperates with public and private organizations in developing technological standards, codes, and test meth- | ods; and provides technical advice services, and information to Government agencies and the public. The Institute consists of I the following divisions and centers: | Standards Application and Analysis — Electronic Technology — Center for Consumer Product Technology: Product j Systems Analysis; Product Engineering — Center for Building Technology: Structures, Materials, and Safety; Building j Environment; Technical Evaluation and Application -— Center for Fire Research: Fire Science; Fire Safety Engineering, j I THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services | designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, ! acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus wthin the exec- | utive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer | languages. The Institute consist of the following divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology. THE OFFICE OF EXPERIMENTAL TECHNOLOGY INCENTIVES PROGRAM seeks to affect public policy and process to facilitate technological change in the private sector by examining and experimenting with Government policies and prac- tices in order to identify and remove Government-related barriers and to correct inherent market imperfections that impede the innovation process. THE OFFICE/FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific informa- tion generated within NBS; promotes the development of the National Standard Reference Data System and a system of in- formation fUialysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure 4hat the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units: /Office of Standard Reference Data — Office of Information Activities — Office of Technical Publications — Library — i Office of International Standards — Office of International Relations. 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. " Located at Boulder, Colorado 80302. 2 8 1977 Corrosion and Metal Artifacts— )C\ A Dialogue Between Conservators and Archaeologists and Corrosion Scientists Edited by B. Floyd Brown Harry C. Burnett W. Thomas Chase Martha Goodway Jerome Kruger Marcel Pourbaix Sponsored by: National Bureau of Standards Smithsonian Institution American University Washington, Conservation Guild Belgian Center for Corrosion Study (CEBELCOR) U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary Dr. Sidney Harman, Under Secretary Jordan J. Baruch, Assistant Secretary for Science and Technology I NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director I Issued July 1977 PREFACE In March, 1976, conservators of cultural property, archaeologists, curators, museum scientists, corrosion scientists, corrosion engineers, and metallurgists traveled from many countries to meet at Gaithersburg, Maryland, in the United States at the National Bureau of Standards. Our meeting was entitled "Corrosion and Metal Artifacts: A Dialogue Between Museum Conservators and Archaelogists and Corrosion Scientists." This volume is the formal report of the proceedings. This meeting in 1976 was the direct outgrowth of the first Rutherford John Gettens Memorial Seminar of the Washington Conservation Guild, held in 1975 at the Freer Gallery of Art on the same topics. The late Rutherford John Gettens was a pioneer in the study of ancient metals, especially the study of ancient bronzes and their corrosion. He set a high standard in a lifetime of work on the technical examination of artifacts. The success of the 1975 meeting was such that the Washington Conservation Guild joined Professor Marcel Pourbaix of the Centre Beige d'Etude de la Corrosion (CEBELCOR) in suggesting that a "Corrosion Week," one in a continuing series of Corrosion Weeks which have been held on both sides of the Atlantic for a number of years, be devoted to the same topic. We are especially grateful to Dr. Jerome Kruger for obtaining the generous support of the Bureau for this meeting and for the publication of these proceedings. The conservators, the scientists, and the archaeologists set the stage for our dialogue with lectures in which they gave their backgrounds and their points of view. The discussions these papers elicited have been included substantially as they occurred. Many of the ideas presented are set down for the first time here. Questions for the structured discussions had been collated by the program committee from questions submitted in advance of the meeting by the participants; the discussion of these questions is given in full, and we hope by reporting the discussion faithfully this report will be a substantial addition to the technical literature which has issued from the laboratories of the world's museums for many decades. Those who would see more of this literature should consult the Art and Archaeology Technical Abstracts, published twice a year by the International Institute for Conservation. We hope that as you read this volume of proceedings you will be carried beyond the methods of conservation and the techniques of the scientific laboratory, however interesting, to consider our fundamental interest in the objects. They represent the material heritage of mankind. These tangible things must be preserved and so our first preoccupation is with the conservation of these objects by the best means we can devise. Solving the problems of conservation is one step, an important step, toward a larger purpose. This larger purpose is the study of man through the things he has made. The study of human culture through material artifacts is gradually becoming recognized as a distinct discipline. It is a discipline to which the skill and insight of the conservator and the instrumentation of the scientist are indispensable, but it is a discipline which has its own structure, methodology, difficulties and rewards; one which demands serious commitment. Those who were fortunate enough to take part in the Dialogue are well aware of the splendid arrangements made for them by Ron Johnson and Paul Fleming of the Institute for Materials Research, assisted by Gloria Serig and others of the Institute Office, as well as Sara Torrence and the other members of the NBS conference staff. We appreciate the efforts of Ellen Ring and the staff of the Institute Text Editing Facility in preparing the copy, and especially those of Rosemary Maddock for preparing the illustrations, laying out the copy and coordinating the preparation (and the editors). This volume contains much material which has not been published before. We hope that the publication of so many useful ideas will prove stimulating to the old hands, and that this volume will be a helpful guide