NOVELTY - A prefabricated body of the plastic (3) and the component (1) surface being passivated (2) are brought together. Exertion of pressure assembles them permanently.    USE - To passivate for example electronic actuating components, protecting them from contamination and mechanical damage, whilst also insulating them. A specific claim is made for an actuator produced, which is used with a fuel injection valve. The component may be a fuel cell (claimed use).    ADVANTAGE - When a piezoelectric component is used to control a fuel injection valve, the need to resist a range of temperatures (-50degreesC to + 150degreesC) dictates use of a silicone-based rubber, of which the precursor is particularly viscous in the non-crosslinked state. This makes passivation by coating or injecting a thin layer, particularly difficult. Further difficulties accrue. The new method is simply applied, overcoming the problem by prefabricating the passivating rubber, which is readily possible, using highly viscous material. The body used, may be non- or only partly vulcanized. This has the advantage, that during crosslinking, it flows into all recesses, completing an intimate covering.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for the electronic component so produced. Preferred features: The body (3) is pre-formed; it is tubular. The internal surface (4) of the body is essentially that of the component, in negative form. The body is formed by at least two individual pieces, each brought together with a region of the component surface. The plastic is partly crosslinked and contains a stabilizing element. The body and/or component surface include a bonding agent. An external device exerts the pressure. It may be caused by crosslinking, especially effected thermally or by illumination. Preferred features of the component so formed include incorporation of a piezoelectric device, which may complete a piezoelectric actuator (1) or a fuel cell.    DESCRIPTION OF DRAWING(S) - A cross section of the covered actuator is shown, the tool exerting pressure being shown schematically.    Piezoelectric actuator (1)    Surface being passivated (2)    Prefabricated plastic body (3)    Electrical connections (6, 7)    Contact terminals (6a, 7a)