DESCRIPTION
TECHNICAL FIELD

This innovation describes the process developed for cadmium plating of internal surface where length of the components are more compared to Internal Diameter (ID).

BACKGROUND OF INVENTION

Cadmium plating plays an important role in a number of key manufacturing areas; Plating activities are essential for controlling corrosion to a predictable, manageable level that does not degrade structure or jeopardize the ability of the airplane to carry its intended design loads. While carrying out cadmium plating on various components fabricated out of different materials it was noticed that uniform deposition was not occurring on internal surface of the components. Due to non uniform deposition, the components were undergoing lot of rejections/Rework which used to consume more time.

This innovation provides the solution for the non uniform deposition by thoroughly studying the present procedure followed.

SUMMARY OF INVENTION

After detail analysis with the expert and processing shop regarding the cadmium plating following points were deliberated

1. Deposition of Cadmium during plating on the Internal Diameter (ID) with less than 10 mm is difficult to achieve.

2. Plating is difficult to be carried out in the deep holes as flow of solution will not be uniform through the depth.

3. Plating cannot be achieved to obtain the required tolerance on the finished part on ID

4. In drawing, it is noticed that close tolerance control is called after cadmium plating on very small internal diameter as well as Outer Diameter (OD) which is very rion economical and difficult to achieve.(Shown in Fig 1)

5. With the experiments on various parts the data was analyzed to find the deposition, From Figure 2, it is clear that as the length of the part increases beyond 2 times the diameter, the plating thickness gets reduced & tend to become zero at the middle of the part.

Based on above observation, to improve the Quality of the cadmium plating on components, following improvements were derived.

a. In the process sheet, the machining allowance were defined correctly to achieve the drawing dimensions on ID and OD of the component

b. To achieve the required plating on the ID of the parts where L/D ratio is more than 2.5 mm, auxiliary anodes were used

c. For achieving better adhesion of cad plating nickel strike (Of thickness around 2
microns) was introduced before cadmium plating.

d. Cadmium plating process parameters like voltage, current, duration etc should be. adhered strictly as per Cadmium plating Standard to achieve required coating thickness on.

DRAWINGS

Fig. 1 Typical.Drawing for cad plating

Fig. 2 Plating Thickness variation with respect to length of parts