Etchtron Chemical Etching Plant

The Nital etch process, in it's various forms, is widely used for the inspection of case hardened steel components to exhibit metallurgical defects such as local re-hardening, burning, cracking and problems arising from grinding or other manufacturing processes.

ETCHTRON 1
This chemical etching plant, as an example of Baugh & Weedon NDT's capability, is designed specifically for the application of the Nital etching process and comprises a series of eight stations together with load and unload stations. All the tanks in this line are manufactured from stainless steel, as this process allows.

The eight active stations include:

1. An acid etch tank containing nitric acid at a typical concentration of 30g/l, in an aqueous solution of isopropanol and a little wetting agent. This station operates at ambient temperature and is equipped with air agitation operated by a foot switch.
2. A cold water immersion tank, with air agitation if required.
3. A de-smutting solution tank. This station is heated for use up to temperatures of 90°C. The tank is fully insulated to minimise heat losses.
4. A cold water immersion tank, with air agitation if required.
5. A neutralising solution tank containing an aqueous solution of sodium carbonate, at a concentration of between 40g/l and 60g/l. This is at ambient temperature, with air agitation if required.
6. A cold water immersion wash tank, with air agitation if required.
7. A hot water immersion wash tank, heated to approximately 100°C. The tank is fully insulated to minimise heat losses.
8. A de-watering oil immersion tank.

Extraction is provided over the nitric acid solution tank, de-smutting station, and the hot water immersion wash station. All stations are provided with manually operated lids. Work pieces are transferred between stations by electrically operated hoists on a monorail.