This paper presents an analysis of the practices of part restoration by metallurgical coatings, based on information compiled from oil refining units in Venezuela and USA.

In all the visited units, parts restoration by coatings has an increasing incidence in the maintenance of rotating and reciprocating machinery; however the corresponding benefits seem to be poorly quantified. Coatings aimed at resisting corrosion and erosion-corrosion use to be carefully selected, mainly for the components of large compressor and turbines. In these cases, the design or selection of the coating is a matter of agreement between materials specialists belonging to the user, equipment manufacturer and/or repair shop; preliminary laboratory and field tests are performed to evaluate the fitness for operation of these coatings. Fewer cautions are taken when the worn area of tribological parts is rebuilt. The decision on the opportunity and modality of restoring is made in the shop and coating selection is governed by criteria of availability, which varies geographically. The assistance of materials specialists is infrequent, most of it occurring in cases of failure. Tribological variations induced by coating's presence, such as modifications of the load carrying capacity in bearing systems or different limits for lubricant contamination with metals, are not taken into account. Existing standards are not sufficient for the proper specification of restoration procedures, as compared with the documentation issued when static equipment are repaired by welding. Non destructive test methods for parts rebuilt by coating are particularly deficient.