Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
  • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel

Definitions

• the defects which are unique to batch-annealed material, are believed to be caused by a trace amount of carbonaceous material that clings to or is associated with the surface of the strip, resists all efforts to remove it by cleaning and pickling procedures used in the mills, and is converted to graphitic material during the batch annealing process.
• obtaining defect free surfaces on tin-free steel strip which is ultimately coated with a finish of chromium metal and chromium oxide is ensured by treating the steel strip, prior to the batch annealing operation, with a minor amount of a substance that is capable of reacting with carbonaceous material on the strip during the batch annealing cycle to convert the carbonaceous material to volatile by-products, believed to be caron disulfide and/or carbon monoxide.
• step No. 4 temper rolling or further cold reducing the strip to about 0.006 inch followed by cleaning essentially as in step No. 4, pickling, usually in dilute sulfuric acid, water-rinsing;
• the metallic chromium coating applied in step 8 will be on the order of about 5-8 mg. per sq. ft. of surface and the chromium oxide film on the order of about 14 mg./ft.
• the chromium and chromium oxide coatings may be applied to the steel strip by conventional techniques such as those described in the article by G. G. Kamm, A. R. Willey and N. J. Linde, Surface and Corrosion Characteristics of Tin-Free Steel-Chromium Type for Beverage Containers, J. Electrochem. Soc.: Electrochemical Technology, pp. 1299-1305, September 1969.
• the active substances present in the aqueous, dilute, preanneal rinse employed in step No. 5 referred to above are generally used in concentrations of from about to about 2500 ppm. of the aqueous medium, preferably about 500 to about 1000 p.p.m.
• the operable substances are of two groups, both, however, within the general class of those compounds which may react with carbonaceous material on the strip steel under batch annealing conditions to form volatile products.
• the first group embodies sulfur-containing compounds which may react with the carbonaceous material to yield carbon disulfide.
• Such compounds are sulfur and the alkali metal and alkaline earth metal sulfates, bisulfates, snlfites, bisulfites, thiocyanates, dithionates, thiosulfates, sulfides and polysulfides, organic sulfides, disulfides, thioethers, sulfoxides, sulfones, sulfate esters and sulfonates.
• Preferred materials from these classes are colloidal sulfur, ammonium sulfide, ammonium sulfate, sodium sulfate, sodium thiosulfate, ammonium xylene sulfonate, sodium sulfide, thiourea, diethylthiourea, potassium sulfate and potassium thiosulfate.
• the second group embodies compounds which may react with the carbonaceous material to yield carbon monoxide during the annealing. Representative of such compounds are the alkali metal and alkaline earth metal oxides and hydroxides and salts that decompose at the temperatures of the batch annealing to form said alkali metal and alkaline earth metal oxides.
• Preferred materials from these classes are calcium hydroxide, sodium hydroxide, barium hydroxide, potassium titanium oxalate, potassium permanganate, sodium nitrite, sodium borate and sodium bicarbonate.
• the annealing chamber containing the panel bundle is charged to an annealing furnace and subjected to the T-l batch annealing cycle (essentially 10 hours at 1185 F. to 1230" F., requiring about three hours to reach said temperatures, and followed by about a twelve hour cooling cycle) under a protective gas atmosphere consisting of hydrogen and 95% nitrogen.
• the panels are coated with a layer of chromium metal (5-8 ing/ft. equivalent to 0.30.5;/. inches) by conventional electro-coating in a typical chromium metal plating solution (M & T Unichrome chrome plating bath) and with a film of chromium oxide (1-4 mg./ft.
• TFS-CT coated control panels are usually rejected because of staining, and adhesion of the coating is poor when subjected to the Scotch tape test.
• TFS-CT coated panels treated according to the invention with special pre-anneal rinse materials are uniform in appearance, without flawed surfaces, and the coatings demonstrate good adhesion.
• a process for preparing chromium-coated steel strip free of surface defects which comprises treating steel according to the following sequence of steps:
• step (g) temper rolling or further cold reducing the steel strip, cleaning as in step (d), pickling, water-rinsing;
• step (e) concentration of the substance in the aqueous medium of step (e) is from about 500 to about 1000 ppm.
• a process for preparing chromium-coated steel strip free of surface defects which comprises treating steel according to the following sequence of steps:
• step (g) temper rolling or further cold reducing the steel strip, cleaning as in step (d), pickling, water-rinsing;
• step (e) 4. The process according to claim 3 wherein the concentration of the material in the aqueous medium of step (e) is from about 500 to about 1000 p.p.m.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Chemical Treatment Of Metals (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22870502

Family Applications (1)

Country Status (13)

Cited By (2)

Families Citing this family (2)

Family Cites Families (3)

• 0
  • BE BE794277D patent/BE794277A/xx unknown
• 1972
  • 1972-03-03 US US00231747A patent/US3756926A/en not_active Expired - Lifetime
• 1973
  • 1973-01-03 ZA ZA730038A patent/ZA7338B/xx unknown
  • 1973-01-04 CA CA160,536A patent/CA991583A/en not_active Expired
  • 1973-01-12 IT IT47660/73A patent/IT976864B/it active
  • 1973-01-15 FR FR7301287A patent/FR2174834B1/fr not_active Expired
  • 1973-01-26 NL NL7301141A patent/NL7301141A/xx not_active Application Discontinuation
  • 1973-02-05 GB GB565273A patent/GB1415394A/en not_active Expired
  • 1973-02-06 BR BR73893A patent/BR7300893D0/pt unknown
  • 1973-02-09 JP JP48015792A patent/JPS48103428A/ja active Pending
  • 1973-02-12 AU AU52070/73A patent/AU466783B2/en not_active Expired
  • 1973-02-28 AR AR246860A patent/AR196911A1/es active
  • 1973-03-02 DE DE19732310565 patent/DE2310565A1/de active Pending

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