New Development in Ion Analysis from Metrohm

Acid pickling is usually the final cleaning stage prior to plating and is the removal of scale (surface oxides) and other contaminants such as dirt and films from chemical immersion. Another benefit of pickling is that the metal surface is activated ready for plating and a light etch is achieved that helps provide a better adhesion to the substrate.

Historically the plating company performed a manual wet titration, 3 times a day, to determine the acid content of the pickling bath and then an excess (approximately 240 litres) of concentrated hydrofluoric/nitric acid was added manually over a 24 hour period to ensure that the acid content of the bath did not fall below a desired limit and hence suitable quality control was maintained.

Metrohm with more than 60 years experience in the field of Ion Analysis has developed a method for determination of the acid content of pickling baths using Ion Chromatography (IC). Metrohm Online IC is designed for continuous 24-7 use throughout the year (with minimal time spent offline for maintenance) that is supplied in an industrial housing and can be custom-tailored to the application. Special control cards show at a glance whether the values are inside the required concentration ranges giving increased security and environmental control.

With the 821 Compact Online IC from Metrohm it was possible to tighten the pickling process and reduce the amount of concentrate added to the pickling bath to ensure that the acid content remains within specification. The Online IC takes a measurement from the pickling bath using a recycling loop every 30 minutes and calculates the acid content based upon the amount of fluoride and nitrate present. Depending upon the result, either no action is taken, or if the acid content is low a defined amount of concentrate is added to the pickling bath using an external pneumatic pump system controlled using an output from the Online IC.

The advantages of the Metrohm Online IC is that there is less human interaction (ideal as the solutions utilised are extremely concentrated acids), a result is obtained every 30 minutes instead of every 8 hours and concentrate is added to the pickling bath only when it is required - when the acid bath falls below 8% - instead of adding excessive amounts of concentrate thereby reducing the running costs of the raw materials.

Dilution of the concentrated acid is performed inline using the time proven Metrohm DosinoT liquid handling technology and a small amount of sample injected onto the separation column required for the Ion Analysis. The Online IC system consists of top class components that have been used for many years in the Metrohm laboratory IC systems and can be operated with ease by non-chemists. No sample preparation is required as the multi-selection valve handles the automation and sampling of the streams of interest.

For the opportunity to discuss tighter process control in an industrial environment using Online IC from Metrohm, please contact 01280 824824 , Fax 01280824800, Email enquiry@metrohm.co.uk