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Passivation

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This ppt include practical learning during Passivation of a cGMP plant.

Published in: Design, Business

Passivation

  1. 1. PASSIVATION Ranjeet Kumar 18 Jul 08
  2. 2. Definition & Mechanism <ul><li>Passivated means de-activated. </li></ul><ul><li>Two very common meanings refer to the </li></ul><ul><li>(A) treatment of stainless steel in nitric acid or other materials to make it less prone to rusting, and </li></ul><ul><li>(B) The application of a chromate conversion coating to zinc or cadmium plating </li></ul><ul><li>Passivation is described as the treating of a metal with a mild oxidant (such as nitric acid) to remove surface iron or iron compounds by dissolution.  </li></ul><ul><li>This action forms a protective passive film (of chromium oxide) on the surface of the metal.  The trace iron left behind from machining and fabrication can provide sites for corrosion if left untreated. </li></ul>
  3. 3. What is undesired in Process Pipes & Why ? <ul><li>free iron </li></ul><ul><li>oxide scale </li></ul><ul><li>rust </li></ul><ul><li>iron particles </li></ul><ul><li>metal chips or </li></ul><ul><li>other nonvolatile deposits </li></ul><ul><li>Exogenous materials in process lines might adversely affect the </li></ul><ul><li>metallurgical or sanitary condition </li></ul><ul><li>stability of the surface, the mechanical operation of a part, </li></ul><ul><li>contaminate the process fluid </li></ul>
  4. 4. Steps of Passivation <ul><li>cleaning the surface with solvents or an alkaline solution to remove organic or metallic residues </li></ul><ul><li>the parts are placed into passivation solutions. The choice for this solution is usually citric acid/ nitric acid. </li></ul>
  5. 5. Range of Key Variables <ul><li>Time – 20 – 120 minutes </li></ul><ul><li>Temp –15 – 80 °C </li></ul><ul><li>Conc – 20 – 50% of Nitric Acid by volume </li></ul><ul><li>Key variables are determined by the </li></ul><ul><ul><li>Types of steel e.g. 316L would have different conditions than 317L. </li></ul></ul><ul><ul><li>Nature of the fluid to be used – </li></ul></ul><ul><ul><ul><li>Industries (Pharma/ Food/ Fine Chemicals) </li></ul></ul></ul><ul><ul><ul><li>Solid content </li></ul></ul></ul><ul><ul><ul><li>Corrosive nature </li></ul></ul></ul><ul><ul><ul><li>Temperature </li></ul></ul></ul><ul><ul><ul><li>Cleaning action </li></ul></ul></ul>
  6. 6. Conformity Test for Passivation <ul><li>To check the effectiveness of the passivation wrt the removal of free iron and other exogenous matter – </li></ul><ul><ul><li>Water Immersion Test. </li></ul></ul><ul><ul><li>High Humidity Test – 24 Hr </li></ul></ul><ul><ul><li>Salt Spray Test – 2 Hr salt spray </li></ul></ul><ul><ul><li>Copper Sulfate Test – The sample is placed into a copper sulfate solution.  Any remaining iron will show up as pink spots. </li></ul></ul><ul><ul><li>Potassium ferricyanide-Nitric Acid Test – Free Iron Test – Ferroxyl Test – Very Sensitive. </li></ul></ul>
  7. 7. Free Iron Test <ul><li>Highly sensitive test </li></ul><ul><li>Used when traces of free Iron or Iron Oxide is objectionable </li></ul><ul><li>Preparation of Solution – </li></ul><ul><ul><li>Distilled Water – 94% (w/w) </li></ul></ul><ul><ul><li>Nitric Acid – 3% (w/w) </li></ul></ul><ul><ul><li>Potassium Ferricyanide – 3% (w/w) </li></ul></ul><ul><li>Use atomizer spray or filter paper and the solution on testing surface. The metal turns blue when iron is present. </li></ul><ul><li>Freshly prepared solution is suggested for the test as this solution has limited performance-life. </li></ul><ul><li>Not recommended for use on products destined for use in Food, & Pharmaceuticals. </li></ul>
  8. 8. Activities at Site <ul><li>Preparing different loops for passivation </li></ul><ul><li>Removing diaphragms of valves, filter cartridges, </li></ul><ul><li>Pressure hold test – using compressed air </li></ul><ul><li>Flushing with ambient water </li></ul><ul><li>Degreasing – 6 hrs with alkaline solution – cleaning of lines </li></ul><ul><li>Passivation – 2 hrs – maintaining a pH of 3.5 for 1 st hr to ensure dissolution of iron particles & a pH of 4.5 for 2 nd hr to stabilize the formation of protective chromium oxide layer. </li></ul><ul><li>Test piece investigation using Free Iron Test. </li></ul><ul><li>Flushing with WFI – to remove all chemicals from the subjected systems – final conductivity of water coming out of the loop should match with conductivity of WFI. </li></ul><ul><li>Reassembling original diaphragms of the valves. </li></ul><ul><li>Leak test. </li></ul>
  9. 9. References <ul><li>http://www.delstar.com/passivating_information.html </li></ul><ul><li>www.sciencedirect.com </li></ul><ul><li>www.techstreet.com </li></ul><ul><li>http://en.wikipedia.org/wiki/Passivation </li></ul><ul><li>www.freepatentsonline.com </li></ul><ul><li>ASME BPE-2007 </li></ul>

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