Methods for passivating stainless steel

a stainless steel and passivating technology, applied in the direction of metal material coating process, etc., can solve the problems of citric acid passivation not reaching the desired effect and significant waste treatment cost, and achieve excellent results, reduce waste treatment costs, and reduce the redox potential
US20040094236A1Inactive Publication Date: 2004-05-20CROWN TECH
86 Cites 12 Cited by

Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
CROWN TECH
Publication Date
2004-05-20
Estimated Expiration
Not applicable · inactive patent

Smart Images

  • Figure 1
    Figure 1
  • Figure 2
    Figure 2
Patent Text Reader

Abstract

Methods for passivating stainless steel after acid pickling treatment in the absence of nitric acid are provided. The methods include the steps of cleaning the pickled stainless steel with an alkaline composition to obtain clean steel, activating the clean steel with an activator composition to obtain activated steel, and passivating the activated steel with a passivating composition in the absence of nitric acid. In the preferred embodiment, the activator composition contains at least one activator, the activator having a significantly higher binding affinity for iron than for chromium as evidenced by their metal complex formation constants.
Need to check novelty before this filing date? Find Prior Art

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 60 / 426,147 filed Nov. 14, 2002, the disclosure of which is expressly incorporated herein by reference.

[0002] The present invention relates generally to methods for passivating stainless steel, and more specifically to pickling and passivation of low chromium steel in the absence of nitric acid.BACKGROUND AND SUMMARY

[0003] The industry standard for pickling stainless steel is to use a hot solution of nitric acid and hydrofluoric acid. Such pickling processes produce hydrofluoric acid vapors and waste nitrates that require special disposal procedures. Alternatives to such processes have been explored, including mechanical abrasion and electrolytic pickling methods. One alternative, disclosed in U.S. Pat. No. 5,821,212, assigned to Crown Technology, Inc., to Peterson (Rinse Aid and Process for Stainless Steel) involves a peroxide-based rinse additive for cleaning stainless steel following pickling wit...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to View More