Analytical Method to Monitor Industrial Pickling Baths Initially Constituted by HF, HNO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;

Brigitte Dustou,Jean-Michel Bergerat,Theodore Tzedakis,Fabien Chauvet,Laure Latapie

doi:10.4236/jasmi.2017.74009

Analytical Method to Monitor Industrial Pickling Baths Initially Constituted by HF, HNO&lt;sub&gt;3&lt;/sub&gt;

Brigitte Dustou, Jean-Michel Bergerat + Show 3 more

Open Access

https://doi.org/10.4236/jasmi.2017.74009

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Abstract

The present study couples the acid/basis titration and the ICP analysis in order to monitor the concentrations of nitric and hydrofluoric acids, and presents into baths used to pickle alloys of titanium or stainless steel, largely employed in the aeronautic industry. The pickling of the alloys releases various metallic cations able to react with HF in order to lead to metal-fluoride complexes and free H+, the last being able to react with the basis. In this study, it was determined: the most significant correlations providing the number of the protons released by the complexation of the metallic cation by the fluoride. The proposed method based on: 1) these correlations; 2) the titration pH = f(VKOH) curves; and 3) the content of metallic cations determined by ICP, enables the monitoring of the content of HNO3 and HF into the pickling bath. Assuming that one bath was used for one type of alloy (alloys of Titanium for example, or alloys of stainless steel), then the proposed method appears providing reliable concentration values of both acids as well as metallic cations.

Highlights

To sum up concerns the stainless steel alloys, taking into account the results of the titrations of the cations released by the pickle of the alloys, we propose the following way to monitor the concentrations of HNO3 and HF into the pickling bath: To access to the nitric acid concentration, the following equation must be used: moles of HNO3 into the pickling bath titrated volume
Acid-basis titration by potash, monitored by pH metry, was chooses and a systematic analysis of the effect of the metallic cations “in majority into the alloys” was carried out, into the ethanol in order to limit the precipitation of the metallic hydroxides
The pH = f(VKOH) curve obtained with an initial composition bath, exhibits two waves respectively attributed to the neutralization of nitric and hydrofluoric acids