PATENT ACT 1970
(39 OF 1970)
COMPLETE SPECIFICATION
(FORM-2)
Title of Invention: - Different stainless steel chemical treatment pickling compounds & processes for the preparation there of.
Name of Applicant: - Mr. Vinay Golwala
Address of Applicant: - 334, Diamond Industrial Estate,
Near Dahisar Toll Naka, W.E Highway Dahisar (East), Mumbai - 400 068
Field of Invention: -Chemical methods for cleaning of stainless steel more particularly to chemical pickling for preparation of brush gel and sprayable gel composition.

Back ground of Invention with regard to the drawback associated with the known art:
The main need for cleaning stainless steel is due to heat treatment, weld scale, iron contamination, rough surface and organic contamination.etc. Different chemical and mechanical methods and sometimes a combination of both can be used to remove the defects mentioned. Chemical cleaning methods reduce the risk of surface contamination. A final cleaning process will often be required to restore an acceptable surface quality with regard to hygiene and corrosion. Chemical methods can remove high temperature oxide and iron contamination without damaging the surface finish,
During the heat treating of steel, oxygen from the atmosphere reacts with the iron in the surface of the steel to form a crust that is made up of a mixture of iron oxides. The scale produced by hot working of steel is formed of iron oxides and other metal oxides, chromium oxide and manganese oxides. So there is need for removal of oxide or scale on the surface of the steel. Numerous methods have been used to remove iron oxides from metal. Pickling is the process of chemically removing metal oxides and iron contamination and scales from the surface of the metal by exposing the oxide layer to inorganic acids and assist the formation of a continuous chromium-oxide, passive film. The rate and extent of pickling depends upon several variables including temperature and acid concentration of the pickling bath.

Pickling involves stain, metal, inorganic contaminants, rust removal and a change or dulling in the visual brightness of the metal. Different acids are used for acid pickling. The concentration and ratio of the acids used in pickling depends upon the plant and type of steel being pickled. Different types of pickling methods are there as mentioned below.
1) Pickling in a bath.
2) Pickling with pickling paste.
Pickling products can be applied in three different ways like brushing, using a pickling gel, spraying using a chemical solution and immersion in a chemical bath. In prior art, the use of pickling for cleaning of stainless steel is described in many patents. US patent no. 6,398,876 is having a method of pickling steel in acid solution in absence of nitric acid is described in the prior art. Pickling process and apparatus for preparation of the same is described in prior art. In prior art, oxidizing and reducing agents are used in the pickling like hydrogen peroxide, sodium sulfate.
The acid pickling of stainless steel is usually performed using fluronitric baths, in which the disadvantage of using nitric acid is that it leads to the formation of nitrous vapours which pollute the atmosphere and soluble nitrates which pollute the liquid effluent. For prevention of nitrous vapours, accelerators are used in the prior art. In prior art, the product formed in liquid form which is having higher reaction rate. So there is need for a process which will have economical limits and reduces pollution

and having controlled reaction rate. The process of acid pickling mentioned in the present embodiment and pickling paste composition formed by using it is a novel acid pickling gel or sprayable pickling gel composition where organic and inorganic viscosity enhancers are used, like polyvinyl pyrrolidone and xanthan gum which decreases the corrosion rate of the metal. In conventional methods the end product of acid pickling obtained is in liquid form which is stored in tanks and for application on steel surface, quantity of the product required is more. In present invention, as the product composition is used in gel or sprayable gel form, so the quantity of product required for application on the steel is less.
In this Invention, in the production of acid pickling gel composition, nitrogen oxide fuming is reduced, by applying this gel form, reaction rate is controlled. This acid pickling composition can be applied by brush or spray. Another advantage of this product is that it can be applied on any shape and size of the surface either by brush or spray without involving conventional immersion system. By application of this gel form of acid pickling composition, it gives uniform, smooth finish to the stainless steel. It helps to stop corrosion and welding scale are removed very easily. This method gives the controlled cleaning of metal. By using this method, self life of the product can be increased so that it doesn't disintegrate.

Object of the Invention:
The main object of invention is that to overcome all the associated drawbacks and to prepare different stainless steel chemical treatment pickling compounds & processes for their preparation.
Another object of the present invention is to produce a composition in such a way that can remove high temperature oxide and iron contamination without damaging the surface finish and assist the formation of a continuous chromium-oxide, passive film and reduces pollution and having controlled reaction rate.
Statement of the Invention:
This is innovative system for preparation of different stainless steel chemical treatment pickling compounds & processes for the preparation there of. The invention mentioned in the present embodiment decreases the corrosion rate of the metal and welding scales are removed. This invention has also economical limits. The advantage of this invention are controlled reaction rate, gives uniform and smooth finish to stainless steel, reduces pollution, controlled cleaning of metal. It can be used for brush application or spray application or dipping application, depending upon product mixture, weight and grades of stainless steel.

Detailed description of preferred embodiment:
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment.
Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or matter.
This present invention relates to acid pickling gel or sprayable gel compositions for metal surfaces and process for preparation of these products. Acid pickling composition containing a novel mixture of ingredients which inhibit corrosion by the acid in the cleaner, corrosion inhibitor additive concentrates for such acid cleaner.
The stainless steel acid pickling gel composition has many advantages.
1) Controlled reaction rate.
2) Removal of welding scales.

3) Reduces nitrogen oxide fuming and controls pollution.
4) Applicable to any shape and size of surface.
5) Reduces economic costs.
6) Uniform and smooth touch to steel.
The acid pickling stainless steel gel composition is used for brush application or spray application or dipping application, depending upon product mixture and weight and grades of stainless steel. The product formed by acid pickling of stainless steel can be applied to any shape and size of surface due to use of this product in two forms. The two forms of this stainless steel acid pickling composition are disclosed in the present embodiment i.e. viscous gel form and sprayable gel form. The gel acid pickling composition product contains 15 - 55% nitric acid by weight, 0.5 - 25% hydroflouric acid, 2 - 15% calcium nitrate, 3 - 16% aluminium nitrate. Synthetic polymers useful in this invention are vinyl based and meet the criteria for nontoxicity and are environmentally safe and degradable. Synthetic polymer used in the present embodiment is polyvinyl pyrrolidone. Gelling agent like polyvinyl pyrrolidone 0.1 - 5%by weight (with suitable cross linking agent) is also added in gel form of stainless steel acid picking composition. PVP acts as corrosion inhibitor as well as a organic thickening agent. So the gel composition is containing with organic thickening agent.

Xanthan gum is added in the reaction depending upon viscosity requirement. Thickening agent is added in gel form of acid pickling composition depending upon viscosity of reaction while in the preparation of sprayable gel composition, organic thickening agent i.e. PVP and inorganic thickening agent xanthan gum are added. In sprayable form, viscosity of the reaction product is low, so there is need of addition of xanthan gum for thickening. This combination of both organic and inorganic thickening agent is used for the first time in acid pickling sprayable gel composition. Optional levelling agents, optional surfactants are mixed together with each other in an aqueous solution depending upon need of the product to improve those properties.
Process for Preparation of viscous gel and sprayable gel
2 - 15% of calcium nitrate, 3 - 16% aluminium nitrate, 0.1 - 5% PVP (Polyvinyl pyrrolidone) solution are taken in container and mixed well by stirrer. Then 15 - 55% nitric acid and 0.5 -25% hydroflouric acid are added while stirring. Polyvinyl pyrrolidone polymerizes the acid solution and forms the gel. A effective rust removing gel composition is formed by the addition of calcium and aluminium nitrate which combines calcium ion and aluminium ion. The inclusion of nitrate ions is found to be effective for cleaning of alloy steels.Afterl5 -30 min. this gives viscous gel containing both organic and inorganic compounds suitable for brush application. For preparation of sprayable gel, nitric acid,

water and PVP solution are added along with xanthan gum to above gel preparation. This mixture is stirred well for 30 min. to 2. hrs. to form spray able gel. Addition of xanthan gum is for increasing the viscosity of the reaction.
The application technique used for application of this product is by brush coating or spray coating. For spray coating techniques, the paste composition is thinned with water and then applied to the metal surface. The composition of the present invention produces excellent pickling and rust removing results.
The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention; which is defined by the scope of the following claims.

Claims
I/We claim,
1. A process for preparation of stainless steel acid pickling
composition comprising of
adding 2 - 15% calcium nitrate and 3 - 16% aluminium
nitrate;
dissolving a acidifier 15 -55% of nitric acid and 0.5 -25%
hydrofluoric acid;
mixing 0.1 -5% polyvinyl pyrrolidone; optionally adding
xanthan gum.
2. A stainless steel acid pickling viscous brush gel composition
formed by process as claimed in claim 1 consisting essentially
of
acid pickling agent such as nitric acid and hydrofluoric acid;
inorganic mixture of calcium and aluminium nitrate;
gelling agent such as polyvinyl pyrrolidone;
optional thickening agent such as xanthan gum.
3. A stainless steel acid pickling sprayable gel composition
formed by process as claimed in claim 1 consisting essentially
of
acid pickling agent such as nitric acid and hydrofluoric acid; inorganic mixture of calcium and aluminium nitrate; gelling agent such as polyvinyl pyrrolidone; thickening agent such as xanthan gum 0.05 - 3%

4. A acid pickling viscous gel composition formed by process described in claim 1, as claimed in claim 2 where the said acid pickling viscous gel composition is formed within 15-30 min by the addition of calcium nitrate, aluminium nitrate, polyvinyl pyrrolidone solution, nitric acid and hydrofluoric acid.
5. A acid pickling sprayable gel composition formed by process described in claim 1 as claimed in claim 3 where the said sprayable gel is formed by addition of xanthan gum to the said viscous gel composition for 2 hr.