遠見化工-PTFE鐵氟龍化學鎳複合鍍

MetChem’s PTFE – Electroless Nickel Composite Deposition

As one of mature surface finishings, electroless nickel is applied to various manufacturing industries due to its high performance in hardness, uniformity, solderability, corrosion and wear resistance. Furthermore, the development of composite deposition does expand the ability of electroless nickel. For example, PTFE/EN composite presents better lubricity and wearability than conventional electroless nickel.

HLHC and MetChem had developed excellent PTFE/EN composite, RoHS compliant chemical with no PFOS and lead- and cadmium-free. The PTFE particles are co-deposited evenly in nickel-phosphorus layer, performs low friction coefficient and wear rate and be suitable for self-lubricating parts.


Electroless nickel (EN), one of mature surface finishing, deposits very uniform nickel-phosphorus (Ni-P) layer and play a key role in manufacturing of industrial, electronic, aerospace, and automotive by its excellent performance to corrosion and wear resistance. Moreover, the composite deposition advances the application of EN. One of the most known composites is PTFE/EN, shows not only good wearability but also desired self-lubricity. PTFE/EN gives finished part a coating which has low friction coefficient and protect the substrate, satisfy the requirement of self-lubricity for mold or bearing.


Lubricity of PTFE/EN

The mechanism of PTFE/EN is that the dispersed PTFE particles in EN bath co-deposit with nickel and phosphorus on surface and forms low friction coating layer as dipping parts into PTFE/EN bath. The left of fig 1. Indicated that dark PTFE particles which helps the lubricity were embedded in Ni-P matrix in microscope observation. According to the past studies[1][2], PTFE/EN performed lower friction coefficient and wear index than conventional EN. Moreover, the co-deposition of PTFE resulted in changing of appearance of coating. The right of fig 1. showed that dull morphology of PTFE/EN compared to conventional EN. However, PTFE is much softer than nickel and phosphorus thus PTFE/EN has lower hardness. But it could be improved resulted from proper heat treatment and remain good wearability.

Fig 1. The microscope observation on the left showed the dark PTFE particles embedded in matrix of Ni-P alloy. On the right showed the dull morphology of PTFE/EN deposition on hull cell.

Fig 2. Charts of varying in hardness and table wear index on EN and PTFE/EN with heat treatment[2].


Key point in PTFE/EN plating

PTFE/EN working bath are made-up by A component of nickel sulphate, B component of reductor agent, moreover, PTFE suspension. Hence the appearance of bath is not clear as conventional and much foam on bath surface. A research1 indicated that the deposit rate of PTFE/EN went down with gaining PTFE level in bath. Once the deposit rate is too fast, PTFE could not co-deposited with Ni-P onto substrate. Thus to plate uniform PTFE/EN coating layer, HLHC suggest to keep slow rate during production. Furthermore, a layer composed by PTFE will form on the top or bottom of the PTFE/EN tank after 2 or 3 days work. Those aggregation of PTFE is not going to dispersed into bath more therefore the bath need to be filtered properly to prevent bath from failure.

In order not to waste excess PTFE is a key to PTFE/EN plating because PTFE is sensitive to aggregate to scrap in bath. Many objects should be considered carefully for good PTFE/EN plating including material, cleanness, and roughness of tank, agitation, pump, and heater. In addition, the maintenance and masking in process also affected PTFE/EN bath life. On the other hand, the quality of PTFE/EN coating is depended to not only bath condition but plating operation. The orientation of parts on fixture, the swing mode of works, pre- and post-treatment, and special rinsing. Those techniques shown as above are closely related to plate even PTFE/EN coating.

Fig 3. Appearance of PTFE/EN working bath.


Analysis method of PTFE content in bath and deposition

In the purpose to plate composite with enough PTFE content, the analysis of PTFE level in bath is frequently and necessary as pH and titration of nickel and hypo. Commonly put the samples of new bath and current working bath into centrifuge, spin 30 minutes to separate liquid and PTFE precipitation. Remove the liquid, drying the precipitation, and weigh the mass to know the PTFE content. And replenishing PTFE by comparison between new and working bath.

Normally the lubricity of PTFE/EN is decided on the content of PTFE in Ni-P alloy, presented by volume percentage (% v/v). The method to measure PTFE in coating is also a high technique. A wildly accepted one way[3] is that weight the total mass of composite deposition. Then dissolve the deposition, filter solution to get PTFE solid, dry it and weigh the mass. After whole process, calculate the result by equation shown as fig 4. with mass and density of Ni-P and PTFE. This method needs high concentration and attention because one small error in procedure will make a dramatic mistake in estimation. Therefore HLHC support an optimal method to customers to save processing time from drying and weight and increase the accuracy based on abundant experience

Fig 4. Equation to calculate PTFE content in deposition.


HLHC, a leading company in electroless nickel from Taiwan, has built solid relationship with customers by passion, expertise, and customization over 30 years. Supply excellent chemical and service of PTFE composite deposition from make-up to, operation, analysis, maintenance, and application. HLHC and MetChem are your dedicated electroless nickel expertise.

[1]:Process and Properties of Electroless Ni-P-PTFE Composite Coatings, Yating Wu
[2]:DOI 10.1179/174329405X40902
[3]:Properties of Electroless Nickel/PTFE Deposits with New Wetting Agents, David Cotty.