Troubleshooting EN

Troubleshooting Electroless Nickel

The following are problems that may occur with electroless nickel plating, plus a listing of possible causes and suggested remedies.

Skip plating, pitting, edge pull-back, step plating, dark or laminar deposit
- Improper Pretreatment - Temperature should be checked as well as purity and concentration of cleaner, activator, and other pretreatment solutions. Some metals and alloys, such as leaded steels, brasses, copper, aluminum and magnesium, require special preparation. Rinsing, temperature and rinsing time should be checked. Consider using an electro-cleaning, ultrasonic cleaning, and/or other methods of cleaning. Minimize transfer times between pretreatment steps. Consider a double zincate process for aluminum work pieces.
- Over stabilization of bath - Bath should be dummied or discarded and replaced. Review replenishment history. Insure adequate work load in the bath, and add additional surface area if needed.
- Chemical contamination - Bath should be dummied or discarded and replaced. Insure no sources of nitric acid, heavy metal or other contamination. Use only proper quality deionized water. Avoid drag-in.
- Improper agitation - Agitation around work pieces should be improved and/or work pieces should be rotated while plating.
- Bath Imbalance - Nickel and reducer should be checked and bath adjusted.
Roughness in deposit
- Particulate contamination from solid particles; i.e. dust, loose nickel or metal chips - Avoid contamination and/or improve workload cleaning and rinsing, and bath filtration. Demagnetize ferromagnetic substrates if possible. Use only proper quality DI water.
- Excessive solution replenishment while work is being plated – Replenishments should be added slowly and mixed thoroughly, as far away from work piece(s) as possible.
- Low stabilizer content. – Increase the stabilizer content in the plating bath.
- Only one side of work affected - Agitation around work pieces should be increased and/or work pieces should be rotated while plating.
- Bath Imbalance - Nickel and reducer should be checked and bath adjusted.
Streaks in deposit
- Improper Pretreatment - Temperature should be checked as well as purity and concentration of cleaner, activator, and other pretreatment solutions. Some metals and alloys, such as leaded steels, brasses, copper, aluminum and magnesium, require special preparation. Rinsing, temperature and rinsing time should be checked. Consider using an electro-cleaning, ultrasonic cleaning, and/or other methods of cleaning. Minimize transfer times between pretreatment steps. Consider a double zincate process for aluminum work pieces.
- Chemical contamination - Bath should be dummied or discarded and replaced. Insure no sources of nitric acid, heavy metal or other contamination. Use only proper quality deionized water. Avoid drag-in.
- Improper agitation - Agitation around work pieces should be improved and/or work pieces should be rotated while plating.
- Low surface area - Surface area should be increased to recommended range.
- Bath Imbalance - Nickel and reducer should be checked and bath adjusted.
Dull or Matte Deposit
- Improper Pretreatment - Temperature should be checked as well as purity and concentration of cleaner, activator, and other pretreatment solutions. Some metals and alloys, such as leaded steels, brasses, copper, aluminum and magnesium, require special preparation. Rinsing, temperature and rinsing time should be checked. Consider using an electro-cleaning, ultrasonic cleaning, and/or other methods of cleaning. Minimize transfer times between pretreatment steps. Consider a double zincate process for aluminum work pieces.
- Chemical contamination - Bath should be dummied or discarded and replaced. Insure no sources of nitric acid, heavy metal or other contamination. Use only proper quality deionized water. Avoid drag-in.
- Bath very old - Bath should be discarded, and new bath prepared.
- Bath Imbalance - Nickel and reducer should be checked and bath adjusted.
- Poor bath control - Uniform temperature should be maintained, pH and replenishment controlled.
Poor adhesion
- Improper Pretreatment - Temperature should be checked as well as purity and concentration of cleaner, activator, and other pretreatment solutions. Some metals and alloys, such as leaded steels, brasses, copper, aluminum and magnesium, require special preparation. Rinsing, temperature and rinsing time should be checked. Consider using an electro-cleaning, ultrasonic cleaning, and/or other methods of cleaning. Minimize transfer times between pretreatment steps. Consider a double zincate process for aluminum work pieces.
- Poor bath control - Uniform temperature should be maintained, pH and replenishment controlled.
- Zincate build up in plating bath - Bath should be used for non-aluminum parts or discarded. Double zincate processing will reduce the rate of zinc contamination.
Poor corrosion and/or chemical resistance
- Improper Pretreatment - Temperature should be checked as well as purity and concentration of cleaner, activator, and other pretreatment solutions. Some metals and alloys, such as leaded steels, brasses, copper, aluminum and magnesium, require special preparation. Rinsing, temperature and rinsing time should be checked. Consider using an electro-cleaning, ultrasonic cleaning, and/or other methods of cleaning. Minimize transfer times between pretreatment steps. Consider a double zincate process for aluminum work pieces.
- Chemical contamination - Bath should be dummied or discarded and replaced. Insure no sources of nitric acid, heavy metal or other contamination. Use only proper quality deionized water. Avoid drag-in.
- Particulate contamination from solid particles; i.e. dust, loose nickel or metal chips - Avoid contamination and/or improve workload cleaning and rinsing, and bath filtration. Demagnetize ferromagnetic substrates if possible. Use only proper quality DI water.
- Improper phosphorous content in the deposit – Adjust plating bath parameters or replace with alternative nickel-phosphorous alloy plating bath.
- Pitting in base metal and/or deposit – Inspect base metal and remedy plating bath as needed.
- Poor bath control - Uniform temperature should be maintained, pH and replenishment controlled.
Slow Plating Rate
- Over stabilization of bath - Bath should be dummied or discarded and replaced. Review replenishment history. Insure adequate work load in the bath, and add additional surface area if needed.
- Chemical contamination - Bath should be dummied or discarded and replaced. Insure no sources of nitric acid, heavy metal or other contamination. Use only proper quality deionized water. Avoid drag-in.
- Excessive solution replenishment while work is being plated – Replenishments should be added slowly and mixed thoroughly, as far away from work piece(s) as possible.
- Improper agitation - Agitation around work pieces should be improved and/or work pieces should be rotated while plating.
- Low surface area - Surface area should be increased to recommended range.
- Bath very old - Bath should be discarded, and new bath prepared.
- Bath Imbalance - Nickel and reducer should be checked and bath adjusted.
- Poor bath control - Uniform temperature should be maintained, pH and replenishment controlled.
Fast Plating Rate
- Particulate contamination from solid particles; i.e. dust, loose nickel or metal chips - Avoid contamination and/or improve workload cleaning and rinsing, and bath filtration. Demagnetize ferromagnetic substrates if possible. Use only proper quality DI water.
- Low stabilizer content. – Increase the stabilizer content in the plating bath.
- Poor bath control - Uniform temperature should be maintained, pH and replenishment controlled.
Short Bath Life
- Over stabilization of bath - Bath should be dummied or discarded and replaced. Review replenishment history. Insure adequate work load in the bath, and add additional surface area if needed.
- Chemical contamination - Bath should be dummied or discarded and replaced. Insure no sources of nitric acid, heavy metal or other contamination. Use only proper quality deionized water. Avoid drag-in.
- Bath very old - Bath should be discarded, and new bath prepared.
- Bath Imbalance - Nickel and reducer should be checked and bath adjusted.
- Poor bath control - Uniform temperature should be maintained, pH and replenishment controlled.
- Zincate build up in plating bath - Bath should be used for non-aluminum parts or discarded. Double zincate processing will reduce the rate of zinc contamination.

Best Practices for EN Plating
for Salt Spray Testing

Best Practices for Quality and Consistency in Electroless Nickel Plating for Salt Spray Testing

Plating EN on panels for salt spray evaluation is a complicated test because of the complexity of the entire process involved in preparing and testing salt spray panels. The following are some of the many factors that can influence salt spray corrosion resistance on any type of electroless nickel, including One-Plate baths; and general recommendations on how to manage these factors. For more information and specific assistance, please contact your Surface Technology, Inc. technical service representative.

Substrate Quality. The incoming surface quality of the part is paramount to produce consistent results. Generally, parts or panels with less sharp edges and smoother surface texture will give better results. Inclusions or impurities in the base metal alloy can lead to failures in salt spray testing that are not due to the EN bath.

Use panels from Green Specialty, Fort Worth, TX https://greenspecialty.com/
Inspect all panels for any irregularities or defects before using.

Age of Electroless Nickel Bath: As EN baths age, the stress of the EN deposit generally becomes more tensile. High tensile stress values can lead to more brittle coatings, which can lead to premature salt spray failures. New EN baths, perhaps due to the faster plating rate, are also known to be less ideal for successful salt spray sample preparation.

Optimal salt spray test results are to be expected between 0.5 and 5.0 MTO.

Phosphorus Content: EN coatings are an alloy of nickel and phosphorus. The amount of phosphorus in the coating is a primary factor in corrosion resistance dictates the crystallinity of the deposit. Salt spray resistance will be higher with higher phosphorus content in the alloy as this makes the coating more amorphous and less crystalline.

Heavy Metal Brighteners/Stabilizers: Heavy metal stabilizers and brighteners like lead and cadmium can cause micro-pitting and porosity of the deposit that can reduce the salt spray resistance of electroless nickel coatings.

One-Plate EN solutions without heavy metals are recommended for optimal results.

Electroless Nickel Bath Control: Need to recommend operating parameters Maintaining pH, temperature, nickel and hypo-concentrations is important for consistent quality deposits.

Operate the EN bath at a relatively lower plating rate capable of producing a phosphorous content on the high end of the specified range. Adjust temperature and pH accordingly.
Ensure proper bath loading according to the specified rage on the data sheet for the EN solution.
Use continual 1-micron filtration at a rate of 10 bath turnovers per hour.
Ensure proper agitation to continually replenish the surface of the parts with fresh EN solution and wash the hydrogen bubbles off the surface of the part while plating, but not so much agitation to cause skip plating.
Work rod agitation or motion of the parts can also be helpful.
Fixture panels for salt spray testing horizontally in a firm rack at a 15-degree angle while in the EN bath. Test the side of the panel that is facing downwards during plating. Mark the side of the panel that is facing upwards during plating as “Do Not Test”.
Keep the bath between 90 – 100% concentration.
- Pumps are an optional method to maintain the bath at a higher and more consistent lever. These are available in semi-automated https://www.walchem.com/ez-series/ or fully-automated https://www.walchem.com/intuition-6-coppernickel/ styles.
- Use of One-Plate single component EN solutions makes bath maintenance easier and more consistent.

Prior to Salt Spray Testing and Evaluation: There are certain common issues that can be incorrectly considered as salt spray test failures. For example, discolorations that are not red rust are not a failure. Red rust at the edges of panels is not a failure, especially if the edges of the panel was not masked before salt spray testing. Red rust from isolated pit areas on panels are likely due to one ore more irregularities in the panels or how they were pretreated, and not an indication that the EN coating is not able to pass the required salt spray testing.

There are also many factors that must be precisely controlled in salt spray testing in order to make the test results reliable, including: humidity, salt content, temperature, timing, part orientation, etc.

Confirm the % phosphorous in the EN coating before sending panels for salt spray testing.
Visual observation of the uniformity of the coating should be verified.
Coating thickness should be verified before attempting salt spray testing.
Masking of the edges of the panels and about 0.25 inches onto the faces of the panels.
Obtain photos of the panels after salt spray testing to verify proper assessment of the results.

Pretreatment: High quality surface preparation is also critical for consistent salt spray results. Excellent alkaline cleaning and acid activation are critical in creating a uniform active surface for the EN initiation and plating. Over-etching the substrate with strong alkaline cleaners (aluminum) or strong acidic solutions (steel) can cause failures in salt spray testing. Avoiding pits in the substrate and coating is very important.

A general process for plating on steel panels for salt spray testing

Use a soft cloth with acetone or other solvent to clean the panels.
Soak Clean.
Rinse
Electroclean in fixtures that make solid contact with the panels anodic or reverse electroclean.
Rinse
30 - 35% hydrochloric acid
Rinse
Electroclean in fixtures that make solid contact with the panels anodic or reverse electroclean.
Rinse
30 - 35% hydrochloric acid
Rinse
2% Ammonium hydroxide in DI water dip.
EN Plating
No post bake

Troubleshooting Electroless Nickel

Best Practices for EN Plating for Salt Spray Testing

Best Practices for EN Plating
for Salt Spray Testing