This paper describes a new application in cultural heritage and other areas for a highly surface specific analytical technique originally developed for semiconductor research. The technique, ultra-low-energy dynamic secondary ion mass spectrometry (uleSIMS), is microdestructive, but has a sensitivity typically better than 1 atom in 10 6 . It can provide an analysis within the top nm, or the top few lm of a surface, and gives chemical fingerprinting as well as atomic composition information. It is complimentary to other near-surface techniques such as SEM-EDX, XRD and electrochemical methods. Here, we describe the use of uleSIMS with SEM and SEM-EDX in a study of the tarnishing of museum silver. We report on the initial stages in the development of reference surfaces for control experiments, and on the data obtained from a lightly tarnished sterling silver test coupon exposed in a museum environment for 2 years. First results from a study of a XVII c. silver fragment, aimed at detecting differences in the tarnish or coating in different areas are also presented. Overall we show that the surface chemistry of all these surfaces is a complex mixture of that due to corrosion, contaminants deposited by solvents, polish media (in an overlayer which may only be a few nm thick), handling and the environment, as well as particulates -both from the environment and from polishes. However, surfaces with different histories show large variations in their uleSIMS spectra and depth profiles, and we attempt to lay the groundwork for the interpretation of these.

In this work, electroless nickel has been deposited onto steel substrates by a selfcatalytic process, which involves temperature and time to create a Ni-P layer with a uniform thickness. The major drawback of electroless nickel is the interdiffusion post heat treatment (PHT) that is necessary to create a metallurgical bond between the steel substrate and the Ni-P deposit. The PHT results in softening of the steel. The aim of this ongoing research is to investigate the effect of introducing a nitrided layer prior to deposition of Ni-P layer, as an attempt to lessen the softening of the steel. To this end, Ni-P coatings were obtained over nitrided and non-nitrided steel substrates. The PHT was done at 400°C or 610°C. The nitrided layer, indeed, avoided the softening of the steel substrate. In addition, the nitrided layer improves the adhesion of the Ni-P coating even when the PHT was done at 400°C.

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In this study, the influence of Al2O3 particle amounts on the mechanical, tribological, and corrosion properties of the composite NiP-Al2O3 coating was evaluated. AISI 4140 steel was coated with NiP through an autocatalytic bath with the addition of Al2O3 particles maintained in suspension by mechanical stirring. Following, the coated samples were annealed at 600 °C to increase the hardness and to create an interdiffusion layer, which improves coating adhesion and corrosion resistance. The coating surface was characterized by SEM/EDS, XRD, microhardness, wear resistance, and corrosion tests. The results showed that the coating particles' amount depends on the bath agitation speed, the sample orientation during the deposition, and the volume of Al2O3 particles in the bath composition. Also, the number of particles in the coating affects the deposition kinetics, the thickness of the interdiffusion layer, which affects the wear and corrosion resistance.

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