Some technical notes regarding the construction of electroless nickel tanks

There are partly very different views about the construction of a suitable electroless nickel tank. Time and again I see in practical life that important prerequisites are not taken into consideration. Because of experiences, revised and better possibilities in the sense of technical progress were developed.

Thus I favour rather freely hanging filter bags which are not within the electrolytes in contrast to the "rigid system" filter cartridge/filter cover. Also the electrolyte pump, which is necessary for the filtration, electrolyte transport and current as well as for the exchange from one to a second container, should be rather a full-immersing staff pump, which revolves/filters the volume 10 to 20 times per hour.

The answer to the question, of which material the tanks should consist, PP or high-grade steel 1.4571, can be gathered from the following conditions that are very similar to those in practice:

one shift mode of operation - > High-grade steel = stainless steel

more than one shift mode of operation - > PP.

I would be happy to explain to you why this situation is as it is. Unfortunately, it is not possible to do it here, since this would take too much space on this homepage.

Heating: Here high-grade steel heating elements 1.4571 have been approved of. Rather angle than staff heating elements as thus the warmth takes a longer way and is better used. With staff heating elements a more intensive heat outlet is necessary in order to avoid overheatings which can lead to nickel particle formations. For dimentioning the capacity of heat the general rule is valid:

Beginning at room temperature the warm up period should not exceed more than 3 to 4 hours in order to achieve the operating temperature. Very important is the heating element surface.

A company wanted to start working with electroless nickel. At that time, when starting the operation, no employee knew anything about this subject. In the workshop stood an old stainless steel container with insufficient equipment and insufficient accessories. To consider the most necessary for the time being the following was recommended:

Electroless nickel system

We are referring to the visit of our Mr. Dr. Dobberschütz and xxx on 12 November 2002 and want to thank you also in written form for the friendly reception at your company.

It was talked in detail about the planned usage of our en process and we would like to take note of the following aspects regarding the technical minimum prerequisites for the constructive design of the electroless nickel plant:

1) Check whether the present stainless steel tank is of the material 1.4571 (V4A). If not, this tank is not suitable. The same applies to the heatings.

2) Build a wall into the tank so that an overflow system is created. From the overflow the bath runs into a free hanging filter bag in the overflow compartment. The filter bag does not have any stainless steel contact. Taking up / hooking of the filter bag with pp-frame. Creating soil discharges in the overflow and electrolyte compartment. The tank can thus be rinsed sufficiently after en but also after nitric acid cleaning.

3) Pump: Bath circulation of total bath volume 10 times/h.

Type of pump: Immersion pump.

Material of tube: Stainless steel 1.4571.

Please, note that there is a sufficient depths for immersion and tube length of pump.

4) Heating: To avoid “overheatings” – en nickel plating of the heaters – with the electrolyte curren tgood Ableitung of the heat must be ensured. Do not exceed the dimesion of 2.0 or 2.3 W/cm2. Check the heater efficiency. Is/are the available heating device/elements sufficient, as e.g. 30 KW need a heating up time of 5-6 hours with regards to 1.200 L bath volume and from RT to required working temperature starting from 88 °C.

5) Filtration: At least 10 times per hour total bath volume. Filter material pp-filter bags, filter unit 1 µm.

6) Protectostate: Starting from a bath volume of 500 L you should consider 2 anodic tank contacts and backplate electrodes each. Arrangements mutual – diagonal in the angles. Both tank contacts and backplate electrodes must be parallely switched, each for itself.

7) Prior to the first application all stainless steel areas which have contact with the electrolyte must be passivated with nitric acid 1:1. Time: 10-12 hours with pump operation at RT.

In case of questions regarding this given information, which proved in practise, contact Mr. Dr. Dobberschütz dialling 0521 / …- Mr. Dr. Dobberschütz will gladly give you advise.