| Title of Invention | ACID RESISTANT COATING COMPOSITION ON STAINLESS STEEL |
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| Abstract | The present relates to techniques for improving the resistance for corrosion to stainless steel. The specific composition invented for acid resistance. The composition or coating media contains Sodium Dichromate as a major constituent and dissolved in Sulphuric Acid and colour of product after coating changes to natural yellow and black. |
| Full Text | THE PATENT ACT 1970 (39 OF 1970) COMPLETE SPECIFICATION (See Section 10 and Rule 13) Application number: 0234/MUM/2006 Composition for Acid Resistance Coating for STAINLESS STEEL PRODUCTS & FASTENERS Satish Garg B 306, Prabhat Tower, Gokhivare, Vasai Road - East, District Thane MAHARASHTRA (INDIA) The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- -1 - The present invention relates to the acid resistance coating for stainless steel products & fasteners. More particular this invention relates to composition used for coating, which gives protection from acid corrosion to metal particularly stainless steel. Objective The aim of developing this composition for coating was to make "Acid Resistant Stainless Steel Products & Fasteners", which can effectively sustain in an aggressive chemical environment than normal bare Stainless Steel Fasteners. Fig l Description BACKGROUND OF THE INVENTION 1. Field of the Invention "Invention is related to make Stainless Steel Full Acid Proof and High Corrosion Resistant". 2. Description of the Invention Fasteners used in power supply batteries are eaten out by the Sulphuric Acid. These batteries are mostly used in Automobiles and for General Purposes. -2- The life of fasteners becomes very short hardly 6 months in acidic & chemical environment; therefore a frequent replacement of fasteners is required. This needs more number of times services, that is a costly affair. Seeing these problems, an innovative coating on Austenitic Stainless Steel has been developed which does not allow items to react with Sulphuric Acid and Stainless Steel becomes full acid proof. SUMMARY OF THE INVENTION In accordance with the present invention, the composition for acid resistance coating for stainless steel products & fasteners comprises of 10 to 15% "Chromium Salt 99% Pure" of Sodium Dichromate or Chromic Acid or Potassium Dichromate, etc. and 20 to 30% Cone. Sulphuric Acid (Sp. Gr. 1.98) and remaining component is De-ionized Water (range 55 to 70%) of composition. More particularly, it has been found that a more desirable composition for acid resistance coating for stainless steel products & fasteners comprises of 14-15% "Chromium Salt 99% Pure" of Sodium Dichromate or Chromic Acid or Potassium Dichromate, etc. and 28 to 30% Cone. Sulphuric Acid (Sp. Gr. 1.98) and remaining component is De-ionized Water (range 55 to 58%) of composition. DETAILED DESCRIPTION OF THE INVENTION Corrosion is a biggest problem to the industry - once material disintegration starts due to corrosion, it is whether by Oxidation or Chemical/Acidic reaction - it has to be replaced. There are two types of Iron based materials - Mild/Carbon Steel and Stainless Steel. Any corrosion resistance in Mild/Carbon Steel is achieved by some coating, which may be either by plating/galvanizing or painting. With the passage of time, coating removal takes place by any of the reason - oxidation, tightening, over torquing, accident, peel off and as a result bare surface is exposed, consequently corrosion starts immediately with a rapid speed. Since Stainless Steel has much higher acid and corrosion resistance than Carbon Steel, so Stainless Steel chosen for aggressive environments like Marine and Chemicals containing Acid Vapors. Stainless Steel has broadly four types of structures - Austenitic, Martensitic, Ferritic and Duplex. Among the Stainless Steel family, Austenitic is the highest usage alloy and its consumption is about 80% of total share of Stainless Steel. This coating is applicable on all Austenitic Grades of Stainless Steel including 200 & 300 series. Internationally, as per IS standards 304 grade is denominated by A2 and 316 by A4. 201 grade does not have any specific denomination/marking as per IS till now. -3- Material disintegration is a material loss whether it is due to corrosion or reaction with the chemical. When fastener (metal) surface is lost, a customer has to replace it with the new one (Fig.5). The Aggressive Chemical Environment where acid is present in the surrounding, reacts with the metal, disintegrate the product and making life shorter of high value product. There huge cost is paid in replacement of parts, labor cost, down time and difficulty of repair. Sometimes, the damaged parts are not available or not possible to repair - a high value product is scraped. This special coating does not allow reaction with the acid and gives a long-life to the product. This coating also gives higher protection to the corrosion. Cost of coating comes Rs. 50/- (1 US $) per 10 kg of Stainless Steel, which is negligible if it is compared with the replacement and labor cost. Process is simple and equipment cost is very low. It can be carried out in one 10x10 sq feet room comfortably. The new acid resistant coating is boon for fasteners, which are in direct contact with sulphuric acid in Battery. Acid Test Procedure Acid resistance performance of coated fasteners is checked by dipping in 1.30 sp gr. of sulphuric acid - there should not be any reaction with the component till 24 hours. In uncoated natural component, reaction is started immediately in 1.30 sp gr sulphuric acid. Acid Test Results Uncoated Natural Finish reaction in 10 minutes. Coated fasteners with above technology not reacting in 24,48, 96 Hours. Salt Sprat ASTM B 117 Method Corrosion Test Uncoated Natural Finish - Salt Spray Hours 250r to 700 Hours. Coated fasteners /sheet with above technology - Salt Spray Hours 300r to 900 Hours. Advantages & Life Cycle Costing (LCC) Analysis This coating for acid resistance is 100% successful & compatible with Austenitic grade. // is partially successful with other grades of Stainless Steel also and for this a further R&D work is continued. 1. Battery consumption is very high and average life cycle of battery is 2 years. So this is a very big saving if special coated fasteners are used in place of natural uncoated fasteners (Fig. 2&3). 2. Chemical Industries & Cane Sugar Mills are continuously emitting acid vapors, where these special coated fasteners are protecting from corrosion and enhancing life of the assembly & product. -4- This coating increases life of the hardware and fixing system of an assembly. For Example, Natural finish Fasteners in Automobile Battery (based sulphuric acid) are eaten by acid within 2 months. A blue/green/whitish colour salt is formed after reaction with the elements present in the Stainless Steel alloy and deposited around the clamp (Fig. 5). It is very cumbersome & costly affair for customer to replace these fasteners frequently. Cost is hardly 10% more after this coating. -5- As per LCC analysis, if uncoated Stainless Steel is replaced even twice during the life- time of a product, coated will be a much cheaper option with a least headache of replacement. Application of Invention in the Fields 1. Austenitic Stainless Products 2. Austenitic Stainless Fasteners The Austenitic Stainless Steel is more popular because: - 1. General Purpose - All Household Utensils are made from Austenitic Grade. 2. Engineering Values - Austenitic is the only grade in steel family where High Tensile Strength is achieved by Cold Working (Forging). Otherwise, high strength is achieved in all steel by heat treatment where lot of problems are envisaged from technical point of view like Galling (Ceasing), Sudden Failures (Breaking). 3. It is more firm during the load at high temperature (800 Oc) as well as low cryogenic temperature (-30 Oc). Sewerage requirement - Acid as well as Corrosion resistant !n sewerage all types of streams are flowing into the drain, for instance, Soap & Detergent (contains free alkali) from homes and Acid from industries. 316 & 304 grades of stainless steel can resist to corrosion but can not resist to acid. The special enviro-coated fasteners in 304 grade developed by Kundan can resist to acid also apart from corrosion and cost is less than 316 grade. This shows that Enviro-coated 304 fasteners are the best solution for the problem in both the types of acid and alkali environment of sewage. This save huge cost, easy servicing and log life. Problems with Hardware Sometimes Fasteners are used in a very aggressive environments like Acid & Chemical and Marine where life becomes short because of corrosion and fasteners are bound to be replaced. If galling (jamming of Nut & Bolt - Fig. 4) takes place, which is a common severe problem observed after corrosion then sometimes whole High Value Product (Assembly) has to be scraped because repairing is beyond the scope of service engineer and this is a very costlier affair to the owner. -6- Fig 4 Permanent Black Colour Fasteners for Automobiles Black Color matching with the counter part at some locations is a requirement of the automobile manufacturers. Black color in Carbon steel is achieved by Zinc plating and life of zinc plating is hardly 6 months. Coating is faded (Brownish/Whitish Color) in next 3 months and looks bad. Coating also comes out by mild rubbing during the use, shining goes off and losing aesthetic in short span. Kundan has developed a special black color coating on Stainless Steel i.e. called "Enviro Coating". It is permanent, having good shining, more corrosion resistant and fully acid resistant with sulphuric acid. This has also lower coefficient of friction and higher anti-galling effect. Anti Galling Molybdenum coating is recommended to avoid galling which is a very costlier. Enviro-coating gives equally good anti-galling effect and replacing to Molybdenum coating. Some areas of Envir-coating application are given below :- 1. Batteries 2. Chemical Industries 3. Marine 4. Building and Construction 5. Water Treatment Plants 6. Water Storage Tanks 7. Cooling Towers 8. Refrigerator & Air Conditioner 9. Washing Machine 10. Heat Exchangers -7- 11. Cold Storage Racks 12. Automobiles Coating Process and Chemical Composition Ingredients 1. Sulphuric Acid 2. Potassium Bichromate (K2Cr2O7) 3. Potable Water Process Equipments 1. Lead Coated Tank Size 2x2x2 Feet 2. Heater with Auto control 90°C ± 5°C Process Methodology 50 Kg of Concentrated Sulphuric Acid is added slowly to 100 Kg of water and then 25 Kg of Potassium Dichromate is dissolved & mixed well. Any of the grades of Austenitic Stainless like 201, 304, 316, etc component (products/fasteners) are dipped in bath for 5 minutes and temperature is maintained 90°C ± 5°C. A white colour of coating with black tinge (2-3 (µ, thickness) adhesion takes place on the component. Then components are thoroughly washed with water and dried in oven for 1 hour at 150°C. These fasteners should be cleaned, free from oil and well polished before coating. Key Words 1. Acid Resistant & High Corrosion Resistant Stainless Steel Products & Stainless Steel Fasteners 2. Acid Proof & High Corrosion Resistant Stainless Products & Fasteners 3. Stainless Steel Fastener for Aggressive Environment 4. Acid & Corrosion Proof Stainless Steel Fastener 5. Acid & Corrosion Proof Stainless Steel Products 6. Chemical Proof Stainless Steel Products & Fasteners 7. Eco Friendly Stainless Steel Products & Fasteners 8. Stainless Steel Acid Proof & High Corrosion Resistant Products & Fasteners References Design Guidelines for the selection and use of Stainless Steel by Nickel Institute {Hand Book Series No. 9014). -8- I claim: 1. The composition for acid resistance coating for stainless steel products & fasteners comprises of 10 to 15% "Chromium Salt 99% Pure" of Sodium Dichromate or Chromic Acid or Potassium Dichromate, etc. and 20 to 30 % Cone. Sulphuric Acid (Sp. Gr. 1.98) and remaining component is De- ionized Water (range 55 to 70%) of said composition. 2. The composition for acid resistance coating as claimed in claim 1 wherein the said "Chromium Salt 99% Pure" of Sodium Dichromate or Chromic Acid or Potassium Dichromate, etc. In the range of ft to 14% and Sulphuric Acid in the range of 22 to 30 % and remaining De-ionized Water of said composition. 3. The composition for acid resistance coating as claimed in claim 1 wherein the said "Chromium Salt 99% Pure" of Sodium Dichromate or Chromic Acid or Potassium Dichromate, etc. in the range of 12 to 14% and Sulphuric Acid in the range of 24 to 30 % and remaining De-ionized Water of said composition. 4. The composition for acid resistance coating as claimed in claim 1 wherein the said "Chromium Salt 99% Pure" of Sodium Dichromate or Chromic Acid or Potassium Dichromate, etc. in the range of 13 to 14% and Sulphuric Acid in the range of 28 to 30 % and remaining De-ionized Water of said composition. 5. The process of coating of the said composition as claimed in claim 1 is Electro-less plating by thermal dissociation of salt. 6. The composition for acid resistance coating as claimed in claim 1 can be used on any of the stainless steel products/fasteners; it is more suitable on Austenitic Grade of 200 & 300 series having distinct advantage in battery fasteners/plates and/also normal engineering application where acid fumes are prevailing in any of the chemical environment. 7. The composition for acid resistance coating as claimed in claim 1, the colour of the fastener/products either remained natural as such and colour also changes to 7 colour rainbow with progress of reaction time to silver white, yellow orange, grey and black. 8. The composition for acid resistance coating for stainless steel products & fasteners according to claim 1 substantially as herein described, expfained and illustrated with reference to the accompanying pictures/ figures. Dated: 17th May 2006 Satish Garg, Applicant and Inventor To The Controller of patents, Patent Office, Mumbai -9- |
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| Patent Number | 272656 | ||||||||
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| Indian Patent Application Number | 234/MUM/2006 | ||||||||
| PG Journal Number | 17/2016 | ||||||||
| Publication Date | 22-Apr-2016 | ||||||||
| Grant Date | 18-Apr-2016 | ||||||||
| Date of Filing | 17-May-2006 | ||||||||
| Name of Patentee | SATISH GARG | ||||||||
| Applicant Address | B 306, PRABHAT TOWER, GOKHIVARE, NEAR EVERSHINE CITY, VASAI (E), DIST:THANE, | ||||||||
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| PCT International Classification Number | C23F11/00 | ||||||||
| PCT International Application Number | N/A | ||||||||
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