We are considering making a protective cover for a transducer electronics out of Polyphenyl Sulfide (PPS) that would require EMI shielding and a decorative finish. Nickel plating, specifically electroless, was proposed to do this. Additionally this cover is in an area where leaks or drips of chemicals, organic solvents from 2pH - 13pH, could come in contact (incidental) with the plated finish and we are concerned about the part maintaining its appearance. Would EN be suitable againast chemical attack? What are the chemicals that could attack or discolor EN?
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Chemical Attack of Nickel Plating 1
- Thread starter usjbh
- Start date
-
1
- #2
I doubt any EN plater will guarantee against “chemicals, organic solvents from 2pH - 13pH,” especially w/o a time frame. Certain organic acids are chelating agents for nickel, maintenance people may use nasties like bleach and ammonia, etc. Most pure organic solvents are pretty harmless, and even halogenated solvents are usually tolerable at room temperature. Chemicals that dissolve Ni, e.g., HCl, may leave a clean surface if rinsed after exposure but develop a greenish corrosion product if allowed to dry. Sulfur-containing compounds can form a black tarnish, especially at higher temperature.
A 4-page table “Corrosion Resistance of Electroless Nickel” is included in EN properties at
“Properties and Applications of Electroless Nickel” from NiDI mentions:
High-phosphorus EN is more corrosion resistant at acidic or neutral pH, while low-P EN in more resistant at high pH. EN is superior to 316 SS in some chemical industry applications. Further, EN provides corrosion and wear resistance to moulds used for plastic and rubber parts. A minimum of 50 microns of high-P EN is used for optimal corrosion resistance. Also,
“Plating of plastic housings for EMI shielding requires many large areas to be covered. Electroless nickel is used in many cases to provide protection against corrosion and tarnishing for electroless copper, which is deposited directly on the plastic housings. Nickel thickness is typically 0.25 to 0.50 micron.”
Elsewhere, it has been claimed that the electroless copper and electroless nickel combination “has the best shielding characteristics of any of the coatings available.”
Due to your corrosive environment, I suggest using 25 microns of a mid- or high-phos. EN, plus passivation in a warm, 0.2% chromic acid solution and/or application of an anti-tarnish sealant:
A 4-page table “Corrosion Resistance of Electroless Nickel” is included in EN properties at
“Properties and Applications of Electroless Nickel” from NiDI mentions:
High-phosphorus EN is more corrosion resistant at acidic or neutral pH, while low-P EN in more resistant at high pH. EN is superior to 316 SS in some chemical industry applications. Further, EN provides corrosion and wear resistance to moulds used for plastic and rubber parts. A minimum of 50 microns of high-P EN is used for optimal corrosion resistance. Also,
“Plating of plastic housings for EMI shielding requires many large areas to be covered. Electroless nickel is used in many cases to provide protection against corrosion and tarnishing for electroless copper, which is deposited directly on the plastic housings. Nickel thickness is typically 0.25 to 0.50 micron.”
Elsewhere, it has been claimed that the electroless copper and electroless nickel combination “has the best shielding characteristics of any of the coatings available.”
Due to your corrosive environment, I suggest using 25 microns of a mid- or high-phos. EN, plus passivation in a warm, 0.2% chromic acid solution and/or application of an anti-tarnish sealant:
- Status
Similar threads
- Locked
- Question
- Locked
- Question
