Product category:
Plating and plating systems
News Release from: Metrohm UK | Subject: Online ion chromatography acid pickling baths
Edited by the Manufacturingtalk Editorial
Team on 23 August 2007
Online ion chromatography controls acid
pickling
Compact Online ion chromatography tightens the pickling process and reduces concentrate added to the pickling bath to ensure that the acid content remains within specification.
A plating company used manual wet titration, three times a day, to determine the acid content of the pickling bath An excess (approximately 240 litres) of concentrated hydrofluoric/nitric acid was added manually over a 24h period to ensure that the acid content of the bath did not fall below a desired limit and hence suitable quality control was maintained
This article was originally published on Manufacturingtalk on 22 May 2008 at 8.00am (UK)
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A more efficient way of controlling the bath is to use ion chromatography.
Metrohm has developed a method for determination of the acid content of pickling baths using ion chromatography (IC).
Metrohm Online IC is designed for continuous 24h/7 day use throughout the year (with minimal time spent offline for maintenance).
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Automated on-line analysis system performs all liquid handling steps such as taking sample aliquots, dosing of reagents, titration and cleaning.
It 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 for the plating company 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 every 30 min from the pickling bath using a recycling loop 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.
To do this, an output from the Online IC controls an external pneumatic pump system.
The advantages of the Metrohm Online IC are as follows.
* There is less human interaction (ideal as the solutions utilised are extremely concentrated acids).
* A result is obtained every 30 min instead of every 8h.
* 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 Dosino liquid handling technology .
A small amount of sample is 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.
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. Request a free brochure from Metrohm UK ...
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