- Email: [email protected]
Stripping anodized aluminum coatings
Shop Problems Plating and Anodizing Use the Shop Problem Card in this issue for free expert advice.
Tarnishing of Silver-Plated Earrings . We plate white metal castings . using a bright cyanide silver ba Q . The problem is that the plated pieces become yellow after a short time. We check the anodic/cathodic area, pK solution concentration, brightener, etc. and everything seems fine. The bath has operated for five months and we have plated about 60,000 earrings. Please tell me how to avoid this problem or if it is possible to protect the silver with a cheap immersion coating. J.C. . There are a number of propri. etary tarnish inhibitors available that will help to prevent the yellowing of silver deposits, which is caused by sulfur-bearing materials. These inhibitors are of three basic types-chromates, mercaptans, or immersion tin deposits. In this case, the organic mercaptans would probably be best in view of the skin contact. Information on these materials can be obtained from one of the companies listed under Silver Plating Processes in
A
the Metal Finishing
MORE
Guidebook and
Directory. (Page 859 in the 1997 edi-
tion.) If the earrings are wrapped in paper or clipped onto cardboard, you should be using a treated paper/cardboard for this purpose. Normal paper/cardboard is manufactured from sulfite pulp, which gives off sulfur enhancing the tarnishing action. Stripping Anodized Aluminum Coatings . I’m looking for information on . removing anodized coatings from aluminum wheels. Any details you can provide would be helpful. P.I. . Although it’s possible to rap. idly remove anodic coatings from aluminum in a caustic solution, there would also be attack of the substrate. Try the solution used for measurement of the coating mass of anodic coatings on aluminum as provided in ASTM B 137. This consists of 20 grams of chromic acid anhydride (CrO,) and 35 ml of 85% by weight orthophosphoric acid per liter of solution. Immerse the part in this solution for 5 minutes at 100°C.
Q A
GRIND OUT PROFIT DOLLARS
You need quick service and fast delivery of coated-abrasive FLAPWHEELS-we need more customers like you-we need each Schaffner is a relatively small and hungry compa will deliver high-quality FLAPWHEELS to you faster than your present supplier. Call us today to start realizing the savings possible from lowering your inventory investment. For all your buffing and polishing needs.
MANUFACTURING PLANTS Emsworth, Pittsburgh, PA (Zip) 15202
I 134
North Delta Dr., Jackson, MS (Zip) 39213
HEADQUARTERS OFFICE Pittsburgh, PA 15202 412-761-9902 FAX: 412-761-8998
This solution dissolves the anodic coating with no significant attack of the substrate aluminum. Be sure to utilize proper personal protection and conduct the stripping under a hood in a well ventilated area. Plating on Tungsten Carbide . I am attempting to electroless . nickel plate a 6% cobalt tungsten carbide material. Using an acid cleaner and metal cleaner blisters sometimes appear, is there a better procedure for electroless nickel plating this material? R.S. A cycle incorporating a Wood’s . nickel strike is suggested. Alkaline clean, alkaline electroclean, 50% by volume hydrochloric acid dip, Wood’s nickel strike, electroless nickel plate. The Wood’s nickel strike is operated at room temperature at a current density of 20 to 200 A/f? for 1 to 4 minutes. A typical strike formulation would include 32 oz/gal of nickel chloride and 16 ozlgal hydrochloric acid. MC
Q
A.
Handbook of Efiluent Treatment and Recycling for the Metal Finishing Industry by L Hmtingn
790 pages $120.00
This bookincludes all aspects of the treatment of efluents arising from various branches of the metalworking andmetal-finishing industries. In sympathy with modem legislative trends, the emphasis is on means of avoiding or at least minimizing the production of effluent. This includes increasing the life process and other baths as well as recycling, whenever possible. Send Orders to: METAL FINISHING
660 White Plains Rd., Tarrytown, NY 10591-5153 For faster scrvicc,call (914) 333-2578 or FAX your order to (914) 333-2570 All ordas must be prepaid Pleaseinclude $5.00shipping and handlii for delivery of each book via UPS in the U.S., 110.00 for each book shipped cxpmss to Cam& and SZO.00 for each bmk shipped express to all other countries.
Circle101 on readerinformationcard METAL FINISHING
l
JUNE 1997
Tarnishing of Silver-Plated Earrings . We plate white metal castings . using a bright cyanide silver ba Q . The problem is that the plated pieces become yellow after a short time. We check the anodic/cathodic area, pK solution concentration, brightener, etc. and everything seems fine. The bath has operated for five months and we have plated about 60,000 earrings. Please tell me how to avoid this problem or if it is possible to protect the silver with a cheap immersion coating. J.C. . There are a number of propri. etary tarnish inhibitors available that will help to prevent the yellowing of silver deposits, which is caused by sulfur-bearing materials. These inhibitors are of three basic types-chromates, mercaptans, or immersion tin deposits. In this case, the organic mercaptans would probably be best in view of the skin contact. Information on these materials can be obtained from one of the companies listed under Silver Plating Processes in
A
the Metal Finishing
MORE
Guidebook and
Directory. (Page 859 in the 1997 edi-
tion.) If the earrings are wrapped in paper or clipped onto cardboard, you should be using a treated paper/cardboard for this purpose. Normal paper/cardboard is manufactured from sulfite pulp, which gives off sulfur enhancing the tarnishing action. Stripping Anodized Aluminum Coatings . I’m looking for information on . removing anodized coatings from aluminum wheels. Any details you can provide would be helpful. P.I. . Although it’s possible to rap. idly remove anodic coatings from aluminum in a caustic solution, there would also be attack of the substrate. Try the solution used for measurement of the coating mass of anodic coatings on aluminum as provided in ASTM B 137. This consists of 20 grams of chromic acid anhydride (CrO,) and 35 ml of 85% by weight orthophosphoric acid per liter of solution. Immerse the part in this solution for 5 minutes at 100°C.
Q A
GRIND OUT PROFIT DOLLARS
You need quick service and fast delivery of coated-abrasive FLAPWHEELS-we need more customers like you-we need each Schaffner is a relatively small and hungry compa will deliver high-quality FLAPWHEELS to you faster than your present supplier. Call us today to start realizing the savings possible from lowering your inventory investment. For all your buffing and polishing needs.
MANUFACTURING PLANTS Emsworth, Pittsburgh, PA (Zip) 15202
I 134
North Delta Dr., Jackson, MS (Zip) 39213
HEADQUARTERS OFFICE Pittsburgh, PA 15202 412-761-9902 FAX: 412-761-8998
This solution dissolves the anodic coating with no significant attack of the substrate aluminum. Be sure to utilize proper personal protection and conduct the stripping under a hood in a well ventilated area. Plating on Tungsten Carbide . I am attempting to electroless . nickel plate a 6% cobalt tungsten carbide material. Using an acid cleaner and metal cleaner blisters sometimes appear, is there a better procedure for electroless nickel plating this material? R.S. A cycle incorporating a Wood’s . nickel strike is suggested. Alkaline clean, alkaline electroclean, 50% by volume hydrochloric acid dip, Wood’s nickel strike, electroless nickel plate. The Wood’s nickel strike is operated at room temperature at a current density of 20 to 200 A/f? for 1 to 4 minutes. A typical strike formulation would include 32 oz/gal of nickel chloride and 16 ozlgal hydrochloric acid. MC
Q
A.
Handbook of Efiluent Treatment and Recycling for the Metal Finishing Industry by L Hmtingn
790 pages $120.00
This bookincludes all aspects of the treatment of efluents arising from various branches of the metalworking andmetal-finishing industries. In sympathy with modem legislative trends, the emphasis is on means of avoiding or at least minimizing the production of effluent. This includes increasing the life process and other baths as well as recycling, whenever possible. Send Orders to: METAL FINISHING
660 White Plains Rd., Tarrytown, NY 10591-5153 For faster scrvicc,call (914) 333-2578 or FAX your order to (914) 333-2570 All ordas must be prepaid Pleaseinclude $5.00shipping and handlii for delivery of each book via UPS in the U.S., 110.00 for each book shipped cxpmss to Cam& and SZO.00 for each bmk shipped express to all other countries.
Circle101 on readerinformationcard METAL FINISHING
l
JUNE 1997