TROUBLESHOOTING GUIDE
PARTIAL, POOR OR NO CHROMIUM DEPOSIT
Possible Causes:
1. Electrical connections
Suggested Remedy: Check all connections, i.e. at cathode, anode, any clamps. Clean and reattach any poor connections. If a connection is hot to the touch it is faulty and adds resistance to the low of current. Be sure connections, cables, or bus bars are adequately sized for the current being used.
2. Incorrect catalyst concentration
Suggested Remedy: Test bath for catalyst (sulfuric acid) level. Lack of any catalyst will produce a brown coating on the part to be plated. If lacking catalyst add required amount of 66o Baume’ sulfuric acid. Reduce excessive catalyst with barium carbonate.
3. Poor racking
Suggested Remedy: Adjust rack or parts to prevent hydrogen gas entrapment. If poor coverage is above a hole, plug with aluminum foil. Eliminate shielding between parts or between parts and anode.
4. Rectifier failure
Suggested Remedy: Check for blown fuses and be sure all phases are on. “Surge” at a higher voltage for a few seconds if meters are fluctuating during plating cycle.
5. Anodes
Suggested Remedy: Clean anodes if covered with heavy scale. Replace if thickness is significantly reduced so that it no longer can carry the current. Reduce distance between anode and cathode. Anode to cathode distances for outside diameters: approx. 4”; inside diameters: approx. 1/2 to 1”. “Dummy” plate to activate anodes coated with yellowish lead chromate.
LOW PLATING RATE
Possible Causes:
1. Low current density
Suggested Remedy: Increase current density
2. Temperature too high
Suggested Remedy: Check temperature with separate thermometer and adjust as necessary. Can also increase current density due to high temperature.
3. Chromium solution out of balance
Suggested Remedy: Test chromium and catalyst levels and adjust as necessary. Low chromium level most common cause.
4. Contaminated bath
Suggested Remedy: Remove dissolved contaminates by electrolysis (porous pot). Reduce trivalent chromium by dummy plating at high temperature and low current density.
5. Electrical connections
Suggested Remedy: Check and repair any poor connections.
POOR ADHESION
Possible Causes:
1. Poor pre-cleaning or rinsing
Suggested Remedy: Adjust cleaning cycle to remove any oil, grease, or oxide scale. Check for ‘water break’ after cleaning. Check rinse water for excessive contamination or too cold.
2. Inadequate etch
Suggested Remedy: Extend etch time. Use caution with cast iron, high carbon steels and do not reverse etch copper alloys.
3. Current interruption
Suggested Remedy: Inspect and correct any loose connections.
4. Anode contact
Suggested Remedy: Use care in lowering parts into the bath. Rubbing against an anode can cause poor adhesion of chrome at the point where contact was made.
ROUGH DEPOSITS
Possible Causes:
1. Poor substrate finish
Suggested Remedy: Rework piece to obtain smoother finish prior to plating. After plating, defects and imperfections in the substrate are magnified.
2. Bath contamination
Suggested Remedy: Filter bath to remove metallic and other impurities which may be clinging to parts upon entering bath. Especially troublesome are magnetic particles.
3. High trivalent chromium
Suggested Remedy: “Dummy” plate with a high anode-to cathode area at plating temperature. If the chromium solution is almost black in color it is usually due to high trivalent level.
4. Excessive reverse etching
Suggested Remedy: Reduce etch time or current density.
5. Bath imbalance
Suggested Remedy: Test chromium and catalyst levels and adjust as necessary.
6. High current density
Suggested Remedy: Reduce current density. If roughness is only on sharp edges or points use “robber” or shield.
PITTED DEPOSITS
Possible Cause:
1. Poor substrate finish
Suggested Remedy: Rework piece to obtain smoother finish prior to plating. After plating, pits in substrate will appear larger.
2. Bath contamination
Suggested Remedy: Filter bath to remove metallic and other impurities, which may be clinging to parts upon entering bath.
3. Improper solution ratio
Suggested Remedy: Test chromium and catalyst levels and adjust as necessary. Chromium/catalyst ratios are typically between 75:1 and 100:1
4. Poor pre-cleaning and rinsing
Suggested Remedy: Adjust cleaning cycle to remove any oil, grease, or oxide scale. Check for ‘water break’ after cleaning. Check rinse water for excessive contamination. Avoid touching areas to be plated with bare hands after cleaning cycle. Begin plating cycle immediately after cleaning.
5. Rectifier AC ripple
Suggested Remedy: Ripple should not exceed 5%.
6. Current density
Suggested Remedy: Adjust current density. Could be too high or too low. Check area of the part carefully and determine amps per square inch. Current density must be set in alignment with temperature, i.e. higher current densities require higher temperatures.
7. Current interruption
Suggested Remedy: Inspect and correct any loose connections.
DULL DEPOSITS
Possible Causes:
1. Improper temperature
Suggested Remedy: Check temperature with separate thermometer and adjust as necessary. Can be too high or too low. Using a current density of 2 amps per square inch temperature should be maintained at /- 2o and in the range of 130 - 140o F.
2. Current density
Suggested Remedy: Adjust current density according to solution chemistry, bath temperature and operating conditions (anode/cathode distance, conforming anode, type of rack, etc). Too low a current density is most common, but could also be too high
3. Current interruption
Suggested Remedy: Inspect and correct any loose connections.
4. Bath imbalance
Suggested Remedy: Test chromium and catalyst levels and adjust as necessary. Chromium/catalyst levels outside recommended ratio of 75:1 to 100:1.
5. Bath contamination
Suggested Remedy: Remove dissolved contaminates by electrolysis (porous pot) or other means. Change bath completely. Especially a result of chloride or iron contamination.
6. Excessive reverse etching
Suggested Remedy: Reduce etch time or current density.
SOFT DEPOSITS
Possible Cause:
1. Bath temperature
Suggested Remedy: Check temperature with separate thermometer and adjust as necessary. Could be a result of too high or too low a temperature.
2. Bath imbalance
Suggested Remedy: Test chromium and catalyst levels and adjust as necessary. Most common imbalance is high chromium level and catalyst outside recommended ratio of 75:1 to 100:1.
3. Insufficient deposit thickness
Suggested Remedy: Increase deposit thickness. If necessary allow for thicker deposit by making part smaller. Deposit should be at least 0.0005” per side (0.001” thick). Thinner deposits will deform with substrate.
BURNED DEPOSITS
Possible Cause:
1. High current density
Suggested Remedy: Lower current density. Excessive current produces a powdery, dull gray deposit especially at edges or points.
2. Temperature too low
Suggested Remedy: Increase temperature according to current density.
3. Anode spacing/placement
Suggested Remedy: Move anode further from part. Use robbers or shields where conforming anodes are to close to high current density areas.
4. Excessive anode length
Suggested Remedy: Change anode so it is slightly shorter than cathode, or mask area of anode that extends beyond cathode.
5. Cathode too high in bath
Suggested Remedy: Lower cathode to about 3 inches below the surface. Hydrogen bubbles breaking near the surface dilutes the solution causing high current density.
6. Bath contamination
Suggested Remedy: Remove dissolved contaminates by electrolysis (porous pot) or other means. Change bath completely. Remove a portion of the bath and replace with new chromium.
7. Low bath concentration
Suggested Remedy: Test and adjust chromium concentration.
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