
Curated with aloha by
Ted Mooney, P.E. RET

The HOTLINE public forum
The authoritative public forumfor Metal Finishing 1989-2025

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0. Choosing a Finish (corrosion, compatibility) |
1. Preparing the part (mech. prep • chem. pretreat • masking & racking) |
2. Metallic Finishing (stainless & titanium • anodizing & light metals • electroplating • electroless plating • PVD & vacuum processes • galvanizing • bluing/black oxide • other inorganic processes) |
3. Organic Finishing (CED, electrocoat • powder coating • lacquers, clearcoats • painting, printing, adhesives) |
4. Post-treatments (chemical post-treats • baking, soldering, drying • stripping & reworks) |
5. Supporting Issues (analysis, lab, QA/QC • water & waste • safety, emissions • plant/process engrg. • specs, books, stats • lingo • metallurgy • precious metal recovery) |
6. NON-industrial (hobbyists, around home • research, thesis • K-12 science • Artists' Corner) |
7. Not quite finishing, but interesting |
Post a Question or RFQ
0. Choosing a finish, corrosion
Reddish brown coating on hand tools - 10/1/25
Anodising or Stannous sulfate - 7/16/25
GI sheet vs. CRCA for rust prevention and corrosion protection - 7/3/25
Coloring Nickel Plating
- 6/7/25
Compatibility of aluminum and brass - 5/16/25
Aluminum posts embedded in concrete
- 5/13/25
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1. Preparation
1a. MECH PREP topics: "Grinding, polishing, vibratory finishing, buffing, honing, blasting"
Rust reappears after sand blasting
- 9/30/25
Deburring of Aluminum components - 9/7/25
What is Shot Peening? - 8/4/25
Furniture maker needs super matte perfectly even surface on aluminum tubing
- 6/2/25
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1b. CHEM PREP topics: "Cleaning, pickling, etching, phosphatizing, activation"
Rust Formation Post Phosphate Pressure Wash - 8/19/25
Yellow to brown stains after zinc phosphate - 8/19/25
Zinc Phosphating Problems & Solutions - 8/5/25
Need Zinc Chloride Wash Station RFQ open to all: Illinois
- 6/2/25
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1c. Capping, plugging, masking, taping
Masking During a Zinc Phosphating and Powder Coating Process - 7/23/25
Dual tone nickel + gold electroplating
- 5/31/25
Masking for Selective Silver Plating
- 3/8/25
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2. Metallic & inorganic finishes
2a. STAINLESS, TITANIUM, CORROSION-RESISTANT METALS PROCESSING
Passivating a nickel-plated part - 10/6/25
Electropolishing surfaces instruction - 10/2/25
Titanium coating on titanium - 9/21/25
Coloring Titanium in an Aluminum Anodizing Line
Inquirer often helps others, so especially deserves our help
- 9/20/25
Electropolishing and Chemical Etching Processes for Cobalt Chromium
- 7/16/25
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2b. ANODIZING AND LIGHT METAL TREATMENTS (Aluminum, Magnesium)
Aluminum Welding Porosity -- Caused by Etching? - 10/14/25
Cloudy surface after clarification in nitric acid - 10/14/25
Chemical polishing defect (anodizing)
- 10/3/25
Type 2 anodize color consistency - 10/3/25
How to Keep Anodized Aluminum Unsealed - 10/1/25
Black/gray pitting after anodize - help? :)
- 9/29/25
Chem Film Rework plan - 9/20/25
Aluminum Anodizing flakes off after heating to 125 °C - 9/17/25
Clear Anodized 6061 -- Black Pitting in Bore - 9/13/25
3D Printed Aluminum Won't Anodize Black - 9/9/25
Magnesium electropolishing and annealing - 8/21/25
Phosphate Contamination in Nickel Acetate Seal - 8/18/25
Clear anodize has a yellow tint - 8/13/25
Rainbow effect / defect on anodized aluminum?
- 8/5/25
Aluminum in the 1930's: "Deplated Finish"
- 7/18/25
New Rectifier Can No Longer Hard Anodize 2XXX Aluminum without Burning - 7/5/25
Zirconization of anodized aluminum - 7/1/25
Ultrasonic rinsing after anodizing - 6/16/25
Black spots /shadow on anodized aluminum corners
- 6/13/25
Anodizing Of Cast Aluminum (ADC12) - 6/12/25
White spots in anodizing of castings - 5/15/25
Anodizing of firearms. Refinishing AR15 receivers - 5/12/25
Passivation of Polished Aluminum - 5/12/25
Excess dye on surface of anodized parts
- 5/3/25
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2c. ELECTROPLATING and ELECTROFORMING
Need CAD finish RFQ Salem VA - 10/14/25
Corrosion of zinc plating after 55 days in transit
- 10/13/25
Gold peel-off over high phosphorus electroless nickel - 10/10/25
Sulfamate nickel plating bath problem with growths - 10/10/25
Electroforming with Brass RFQ: Vadodara India - 10/10/25
Raising tensile strength in Nickel Sulfamate bath 2nd Rqst - 10/10/25
Zamac with high porosity; process is not able to cover the pores - 10/3/25
Acid Zinc Plating is Shiny & Bluish
- 10/3/25
Egg Albumin concentration as electroforming separation aid? - 10/1/25
Plating Pd or Au on smooth polyimide film RFQ open to all: Minnesota - 10/1/25
Using Pre-Plated BeCu - 10/1/25
Boric Acid and Nickel Plating - 9/24/25
Ni-Cr Plating on Diecastings Blistered - 9/23/25
Black spots after copper coating - 9/22/25
Need solar absorber coatings -- black chrome or blue sputter coat RFQ open to all: Colorado - 9/21/25
Can you rework an ID on a titanium part by plating? - 9/20/25
Gold plating of 440A - 9/10/25
Random growths dots on Hard Chrome plating in HCD area
- 9/9/25
Need Phosphor Bronze Plating Service RFQ open to all: California - 8/27/25
Copper is spontaneously depositing on rotogravure cylinders
- 8/21/25
Thickness of copper strike when nickel plating diecast - 8/19/25
Tin plated parts are turning black - 8/14/25
Copper plating onto Silver isn't adhering properly - 8/6/25
How to nickel plate aluminum with good adhesion? - 8/5/25
Nickel-boron plating pitting problem in MEMS probe card
- 7/31/25
Alkaline Zinc Barrel Plating -- Suggested current & time - 7/23/25
Copper plating steel grounding (earthing) rods - 7/23/25
Stain marks found on matte tin surface
- 7/3/25
Nickel plating zamac die castings for bathroom fixtures - 7/1/25
Heavy Bronze Plating Is Delaminating
- 6/25/25
Acid zinc plating Anodes - 6/20/25
What is the Composition of EPNS silverware? - 6/16/25
White streaks/patches, and spots, after Nickel Plating
- 5/31/25
Blue Color Powder on Silver Plated Parts
- 5/30/25
Acid Zinc Bath Contamination
- 5/25/25
Titanium-Cadmium Plating Q&As, Problems & Solutions - 5/24/25
Acid zinc plating: Non coverage problem
- 5/13/25
Gold/yellowing on non-chromated zinc plated Hull Cell panels - 5/13/25
Glycol contamination in alkaline zinc bath - 5/13/25
Alkaline zinc plating bath: How to remove carbonates: FAQs + Q&A Forum - 5/9/25
Electroplating wire with zinc/tin for Garment hangers
- 5/7/25
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2d. ELECTROLESS PLATING, PLATING ON PLASTICS, IMMERSION PLATING, CHROME-LOOK SPRAYS, LIQUID METAL COATINGS
Recubrimiento acero alto carbon / Coating high carbon steel - 10/10/25
Problems Chrome Plating ABS Plastic
- 7/13/25
Mirror finish spray chrome - topcoat yellowing - 7/6/25
Waviness problem in Nickel Chrome Plating on ABS Plastics
- 5/18/25
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2e. PVD, CVD, ION IMPLANTATION, VACUUM PROCESSES
2f. GALVANIZING, ALUMINIZING, HOT TIN DIPPING
Eliminate foam in galvanizing line - 10/17/25
How to calculate/measure the thickness of zinc coatings - 9/16/25
Triple Salt and Quadra Flux Densities? - 6/23/25
How to reduce shine of galvanizing - 6/5/25
Hot-Dip Galvanizing Kettles: how to build - 5/30/25
Hot-Dip Galvanizing: best Nickel and Aluminium content?
- 5/13/25
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2g. BLACK OXIDE, BLUING, COLORING, PATINAS
2h. OTHER INORGANIC FINISHING: Mechanical Plating, Nitriding & QPQ, Metal Spray, Zinc-rich Dip-Spin Coatings, Sherardizing, Rust Preventatives, etc.
Nitriding/QPQ Assistance Please - 8/4/25
Geomet 750 Hp galvanizing - 8/6/25
Ferritic Nitrocarburizing has red color to it?
- 6/15/25
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3. ORGANIC FINISHING [PAINT, POWDER COATING] . . .
3a. ELECTROPAINT PRIMING, AUTOPHORETIC COATINGS
Electrodeposition/e-coating (CED) issues & problems - 9/20/25
Foam deposition on E-Coat/CED Parts - 7/24/25
CED coating process questions
- 7/16/25
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3b. POWDER COATING
Checklist for Powder Coating Preventative Maintenance - 9/10/25
Powder coating as maskant for Class I EN plating
- 8/18/25
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3c. LACQUERS, CLEAR COATS, ELECTROPHORETIC TINTING, ANTI-TARNISH
Steel sealant for cold rolled countertop
- 3/13/25
Want anti-pit solvent for Electrophoretic Lacquer
- 12/4/24
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3d. PAINTING, PRINTING, ADHESIVES AND OTHER ORGANIC COATINGS
4. POST-TREATMENTS
4a. CHEMICAL POST-TREATMENTS [CHROMATE CONVERSION COATINGS, RUST PREVENTATIVES, PATINAS, COLORIZING]
Anti tarnish for copper coating on imitation jewellery - 9/20/25
Black zinc plating/chromate turns green - 9/11/25
Olive drab Chromate Coating
- 6/6/25
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4b. BAKING AND NON-CHEMICAL POST-TREATMENTS [HYDROGEN EMBRITTLEMENT AND DE-EMBRITTLEMENT, ANNEALING, WHISKERS, SOLDERING, REFLOWING]
Hydrogen Embrittlement of Zinc Plated Wishbones?
- 9/9/25
Hydrogen Embrittlement in Plating
- 4/28/25
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4c. STRIPPING, REWORKS, ETC.
Stripping Nickel From Kovar - 7/25/25
Removing/stripping TiN (Titanium Nitride) coatings
- 5/18/25
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5. SUPPORTING ISSUES
5a. ANALYSIS, LAB TECHNIQUE, Q.A., SALT SPRAY TESTING
Analyze Chrome Plating Bath; Determine sulphates - 9/25/25
Zinc coating thickness vs. salt spray resistance - 9/23/25
Determination of hexavalent Chromium in Trivalent Chrome Plating solution - 6/17/25
What wavelength for testing Bonderite T-5900? - 6/2/25
Caustic Analysis -- Free Alkali vs. Total Alkali - 5/16/25
Analysis of alkaline zinc plating bath
- 5/3/25
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5b. WASTE & WASTEWATER TREATMENT, POLLUTION CONTROL
Removal of Ammonia from Wastewater - 7/23/25
Spot test for cyanide in waste water
- 1/26/25
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5c. SAFETY ISSUES, EMISSIONS, TOXICITY, ENVIRONMENTAL IMPACTS
Is boric acid toxic? - 8/18/25
Health risks of smoking near nickel plating solutions
- 7/28/25
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5d. PLANT & PROCESS ENGINEERING, CONSTRUCTION
Need Racking Machine - Endura - 10/10/25
Algae, and Ventilation of Boric/Sulfuric Anodizing BAC5632
Inquirer often helps others, so especially deserves our help 2nd Rqst
- 9/25/25
Brass V-blocks Overheating During Chrome Plating - 9/21/25
Hanson - VanWinkle - Munning (H-VW-M) / M & T Chemicals memories & memorabilia - 9/13/25
Barrel plating dangler problems and alternatives
- 9/13/25
Why Anodizing Uses a Hollow Copper Work Bar - 7/1/25
Cooling the Hot DI Seal after Anodizing for Deionization - 5/7/25
Cleaning up Chromic Acid Surface Contamination
- 4/20/25
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5e. QUESTIONS ABOUT SOFTWARE, SPECS, BOOKS, EDUCATION, INDUSTRY STATS, HISTORY, ETC.
Specification DS30000 - 7/23/25
Questions about military finishing spec. MIL-STD-171? - 5/24/25
Specification VW 13750
- 5/13/25
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5f. W...W...W...WORD OF THE WEEK
5g. MOSTLY METALLURGY; Heat Treatment
3d printed Inconel 718 part turns blue in vacuum heat treatment
- November 16
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5h. METAL RECOVERY
Recycling gold from scrap PC boards - 10/15/25
Is this ore/rock Platinum, Palladium & Rhodium? A meteorite? - 10/2/25
Iridium Extraction from Coated Titanium Anodes - 8/5/25
Reverse electroplating for platinum recovery - 7/2/25
How many computers for one ounce of gold? - 6/24/25
Removing/Reclaiming Gold plating from watches, flatware, wheels
- 6/9/25
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6. NON-INDUSTRIAL ISSUES
Hobbyists, DIY, Around Home
Nickel Plating Antique Wood Stove is Unsuccessful - 10/14/25
Brass electroplating for amateurs & students
- 10/10/25
Steelcase Tanker Desk Restoration Tips - 10/5/25
304 Stainless Steel heat coloring inconsistencies - 10/1/25
Need Gillespie Antique Restorer - 9/27/25
How to tell whether its blued or painted - 9/27/25
Removing oxidation from bronze gravemarkers - 9/13/25
Damaged finish on copper table - 9/3/25
Why is this penny silver?
- 8/30/25
Green bubbling from silver plated brass cane handle
- 8/21/25
Need info on zinc brightener - 8/18/25
Protection for outdoor sculptures and statues - 8/6/25
Sawdust Patination Technique for Large Objects - 8/6/25
Painting cast iron fountains, Restoring rusty fountains - 8/3/25
Nickel plating my Taurus pt92 AF - 8/3/25
Penny isn't copper color - what do I have? - 7/26/25
Remove Water Stain from Teak - 7/11/25
Copper/Aluminum interaction problem in swimming pool - 5/25/25
Need White Gold Plating on a Ring RFQ open to all: Louisiana
- 5/16/25
White Gold Ring vs. Sterling Silver Ring
- 5/1/25
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6b. RESEARCH, THESIS TOPICS, UNIVERSITY & POST-GRAD STUDENTS
Chemical Drop/Black Spot on Alkaline Zinc Plated Part
- 9/8/25
Pure Cobalt Plating Problems & Solutions - 8/21/25
How to Calculate Plating Rate - 7/31/25
Need 20µ gold or silver coating on 50µ dia. spherical magnets RFQ open to all: Southampton, UK
- 5/7/25
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6c. K-12 Science Projects, Grammar & High School Student Questions
6d. The Artists' Corner
Restoring Bronze Statue
RFQ open to all: Maryland
- 9/9/25
Protecting copper work for a gallery exhibition
- 9/1/25
Need gold plating of small objects RFQ: Brooklyn, NY
- 8/7/25
Emmy is corroding and flaking
- 5/5/25
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7. DRIFTED OFF FINISHING, BUT INTERESTING :-)
Toxic effects of boric acid on animals from ants to feral cats - 9/17/25
It's not a lamp base, it's a font holder
- 9/9/25
Need sweet spirits of nitre (the traditional folk medicine) - 8/20/25
Sterling silver vs. silver plate -- How to tell?
- 7/5/25
Want Stiffel Lamp to Work RFQ open to all: Washington, USA - 7/1/25
Removing rust on Buddy L pressed steel car - 6/23/25
Copper Tubing for Internal Natural Gas? - 6/16/25
Antique iceboxes & refrigerators - 6/9/25
Barber Chair Restoration Q&A's and Successes
- 6/2/25
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