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Q1. |
Rhodium plated no white enough even when new make up. |
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(1) |
Contamination |
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Contaminants from: |
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New plating tank, new hose, contaminated D.I. water, low grade conc. Sulphuric
acid Use carbon treatment 5g/l for 1 hour with constant stirring. |
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(2) |
Inadequate sulpuric acid |
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Analyze acid content and add to optimum level. |
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(3) |
Improper working parameter: |
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Temp too low – raise temp to 45℃ |
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Plating time too long, suggest under 60seconds |
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Rhodium content too low(<0.5g/l) or too high (>3g/l) |
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Current density too low (little gas bubble from cathode is normal during
plating) |
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(4) |
Undefined reason |
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Carbon treatment gives better result in most cases. |
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Q2. |
Deposit is white just after plating but change to black later. |
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Inadequate plating time result in partial coverage |
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Reaction between substrate and moisture in air or packing material. |
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Heavy contamination, rhodium layer not pure. |
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Problem in under-layer, check & fix. |
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Packing paper is acidic |
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Q3 |
Rhodium plated not white enough, dull. |
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Rhodium content too low, raise to optimum. |
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Acid too high, dilution. |
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Metallic contamination, use RHP-20 purifier |
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Mix with other brand Rh solution, |
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Acid build up, acid content will decrease gradually after using RD-A1 |
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Undefined reason, add AS-900 additive W can improve brightness anyway. |
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Q4 |
Black spot at deposit. |
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carbon treatment can remove |
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Q5 |
Pt/Ti anode change to black. |
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High acid attack or use too long, change new anode. |
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