A method of manufacturing a sensor (1), such as a corrosion sensor, a mask including a series of masking elements (21, 22, 23) for masking a corresponding series of sensing elements (12, 13, 14), a sensing element having such a mask and a sensor are provided. The sensor (1) includes a number of metallic strips (12, 13, 14) mounted on a non-conducting substrate (9) and a module (3) for forming electrical connections to the strips whereby to enable communication between the strips (12, 13, 14) and monitoring equipment for the sensor (1). The module includes a number of wire connections (15, 16, 17, 18) and the method includes the steps of encapsulating the wire connections within a flexible chemical and heat resistant sealing compound and subsequently encapsulating the flexible sealing compound within a second sealing compound by an injection molding process. The sensing elements (12, 13, 14) are covered by the masking elements (21, 22, 23) prior painting the sensor (1) with a corrosion-inhibiting paint. The masking elements (21, 22, 23) are made of a material allowing only weak adherence of paint in order to have sharp paint edges around the sensing elements (12, 13, 14). Sharp edges allow the corrosion-inhibiting agents to leach onto the sensing elements (12, 13, 14).