Cleaning and liquid contact with solids – Processes – For metallic – siliceous – or calcareous basework – including...
Patent
1997-01-07
2000-03-07
Marschel, Ardin H.
Cleaning and liquid contact with solids
Processes
For metallic, siliceous, or calcareous basework, including...
134 2, 134 4, 134 6, 134 10, 134 11, 134 19, 134 26, 134 28, 134 41, C23G 102
Patent
active
060334851
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the acid pickling of metallic materials, especially ones made of alloy steel, stainless steel or titanium alloys.
According to a process which is known, especially from FR-A-2,587,369, the pickling of steel materials is performed in a bath consisting of an aqueous solution containing ferric ions and hydrofluoric acid. This bath has the advantage of not containing nitric acid and therefore of not generating toxic compounds derived from nitric acid during pickling.
As a substitute for hydrofluoric acid, which may be dangerous to handle, it has been proposed in FR-A-2,657,888 to use organic acids which are not iron-oxidizing agents, especially formic acid or acetic acid.
Other inorganic acids, such as sulphuric acid or phosphoric acid, may also be used in making up such pickling baths.
It is known to carry out the pickling of the surfaces of metal components by immersing the components in baths of the aforementioned type. During pickling, the baths may be regenerated by introducing an oxidizing agent so as to increase their life. To do this, air or an oxygen-containing gas is bubbled into the bath, or else a more powerful oxidizing agent than gaseous oxygen, such as ozone, hydrogen peroxide or a compound of the peroxide, peracid or persalt type, may be introduced.
However, especially in the case of the continuous pickling of strip, the pickling of wire or the pickling of components, the pickling kinetics may be too slow and require the plant to be expensively tied up for an excessive period of time.
In order to increase the pickling kinetics appreciably, it is known to apply the pickling solution by spraying it onto the surface of the said metal component: thus, the solution in contact with the surface to be pickled is continuously being replenished, while at the same time the pickling residues are being removed very rapidly.
According to a conventional process, the pickling solution is sprayed onto the component to be pickled and the solution, after it has come into contact with the component, is recovered and recycled in a closed pickling-solution circuit. The solution is usually regenerated by bubbling air or an oxygen-containing gas in at one point in the pickling-solution recirculation circuit.
In industrial pickling processes, these operations are undertaken in a closed spray chamber in which the components to be pickled lie. Under these confined-atmosphere pickling conditions, it has been observed that, although the pickling rate with the said sprayed solution was initially much higher than that in immersion pickling, this improvement disappeared after a few hours and could not be maintained throughout the life of the said solution, this being so despite the regeneration of the solution by bubbling air or oxygen in.
The efficacy of the process thus rapidly returns to being comparable with, or even inferior to, that of an immersion process.
The object of the invention is to provide a process for the-acid pickling of metal components using spraying, in which process the pickling rate is significantly improved throughout the period of use of the same solution.
In order to maintain the pickling rate with the said sprayed solution at a high level, it is possible to add a powerful oxidizing agent, especially hydrogen peroxide, to the pickling solution.
However, such oxidizing agents, especially hydrogen peroxide, have the drawback of being expensive.
The object of the invention is also to improve, in a particularly economical way, the pickling rate in processes of the aforementioned type.
To this end, the subject of the invention is a process for the pickling of metallic materials, especially ones made of alloy steel, stainless steel or titanium alloys, using a pickling solution S containing ferric ions in acid medium comprising at least one acid chosen from a haloacid, especially hydrofluoric acid, an inorganic acid, especially sulphuric acid or phosphoric acid, and organic acids which are not iron-oxidizing agents, especially formic acid or acetic acid, in whi
REFERENCES:
patent: 4097271 (1978-06-01), Swinkels et al.
Didier Paul
Vialatte Bernard
Marschel Ardin H.
Usinor
LandOfFree
Process for the pickling of metallic materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the pickling of metallic materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the pickling of metallic materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-359008