Electroless Nickel for Corrosion Control in Chemical, Oil and Gas Industries

Abstract

The electroless nickel (EN) coatings (a group of coatings) have truly unique engineering properties -uniformity in thickness, high corrosion resistance, high hardness (500 to 900VHN), good wear resistance, inherent lubricity, easy solderability and brazeability, adjustable electric and magnetic properties. These unique properties are due to the nanocrystalline nature of the deposits, e.g. in EN nickel-phosphorous deposits grain size range between 10-12 A° to 150 A° (1-1.2 to 15 nm) depending on the phosphorous content in the deposit. Corrosion resistance has been one of the primary attributes of EN coatings. EN is a barrier coating, protecting the substrate by sealing it off from the environment. The corrosion resistance is further enhanced by the formation of glassy passive oxide film on the coating surface. The higher phosphorous (10 to 12 % P) EN coatings are more resistant to acidic corrodents and products that hydrolyse to form acids. Lower phosphorous (1 to 4 % P) EN coatings are very resistant to strong alkalis. EN can withstand the corrosive environments encountered in oil and gas wells and more importantly the "holidays" (pores and scratches) are not the sites for accelerated corrosion even when sulphide is present in the crude oil. EN coatings are being successfully used for corrosion protection of all the 'boiler works' -heat exchangers, compressors, valves, ducts etc. against corrosive fluoride vapours by the French Atomic Energy Commission. EN coated spheroidal graphite iron and lead connectors and fittings are being commercially used for combating corrosion, the former in the natural and LP gas industry and later, as cost effective replacement for DZR brasses which 155 Brought to you by | Purdue University Libraries Authenticated Download Date | 5/26/15 12:15 PM were sometimes prone to dezincification and bacterial corrosion. EN coatings exhibit resistance to S.C.C., a phenomenon that had caused catastrophic failure of steel in high temperature caustic and chlorine service. The successful applications of EN for corrosion protection depends on the proper surface pre-treatment, high performance and properly controlled operation of the selected EN plating bath and the conformance to specifications/standards. All these factors are described in detail for maximising the corrosion resistance performance of EN coatings. A number of successful cases on the use of EN coatings in the industry are described in the paper. Brought to you by | Purdue University Libraries Authenticated Download Date | 5/26/15 12:15 PM

Tuning Interface to Improve Corrosion Resistance of Electroless Ni-P Coating on AZ31B Alloy

“…It is evident that the coatings have grains in nano-crystalline size. Available previous reports showed similar results and the broad diffraction pattern was interpreted as (1 1 1) plane of a face centered cubic phase of nickel with crystallite size of 1.2 nm [29,30]. Chemical composition of the coatings from EDX measurements demonstrated a phosphorus content of 3-4 wt % in both the two coatings.…”

Electroless deposited Ni–P alloys: corrosion resistance mechanism

“…20 at.% P (close to the eutectic composition) exhibit distinctly better corrosion resistance than does pure Ni, showing a suppression of anodic dissolution in the potential range where pure nickel dissolves actively in acids [10][11][12][13][14][15][16][17][18][19][20][21][22]. This holds for melt spun [10][11][12], electroless [13][14][15][16] or electro-deposited [17][18][19][20][21] Ni-P alloys. It is also generally accepted that only X-ray amorphous or nano-crystalline alloys-irrespective of mode of production-exhibit this superior corrosion resistance [18][19][20] whereas (re)crystallization neutralizes this effect [13,30].…”

Development of a high-range gamma ion chamber for space critical applications

“…The HV electrode is a highpurity alumina ceramic tube of 15 mmID Â 20 mmOD Â 36 mm length made conducting by nickel-plating on the inner diameter of the ceramic tube. The nickel-plating was carried out by Materials Processing Division of BARC [3,4]. The ceramic tube is rested at one end on a stainless steel (SS) end plate while the other end of the tube is in contact with SS disc, which is connected to C/M feedthru.…”