锌酸盐镀锌镀层起泡的原因综述

分析了锌酸盐镀锌层的起泡问题,将其产生的原因归纳为表面不洁、镀层应力及工件渗氢3类,提出了相应的解决办法。     

Effects of 2-buthyne-1,4-diol additive on electrodeposited Ni films from a Watts-type bath

Structures of Ni films electrodeposited from a Watts-type bath containing 2-buthyne-1,4-diol (BD) were investigated using SEM, cross-sectional SIM, XRD measurement with a pole profiling technique and electrochemical methods for controlling properties of Ni electrodeposits. Preferred orientation of Ni electrodeposits was assigned to potential domains for electrodeposition. Preferred orientation in the higher potential region was (1 1 0) or (1 0 0), that in the middle potential region were (1 1 1) and (3 1 1), and that in the lower potential region was (1 0 0). The growing axis of Ni electrodeposits seems to agree with the speculation from Pangarov's model based on the two-dimensional nuclei theory in the lower overpotential region in which the dominant growing plane is fundamentally determined by crystallization overpotential related to supersaturation of adatom, although the growth axes of Ni deposits do not always agree with the preferred orientation. For example, preferred orientation of (1 1 0) was assigned to growing (1 1 1) plane which tilts at 55° to the substrate. Adsorption of BD affects the structure and morphology of electrodeposits via an inhibitory effect related to its surface coverage depending on surface orientation, growth rate and BD concentration in the plating bath.     

Corrosion resistance properties of electroless nickel composite coatings

Electroless nickel (EN) composite coatings incorporated with PTFE and/or SiC particles demonstrated significantly improved mechanical and tribological properties as well as low surface energy which are desired for anti-sticking and wear resistant applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. This work aimed to investigate the corrosion characteristics of EN composite coatings using electrochemical measurements which include open circuit potential (OCP), electrochemical impedance spectroscopy and potentiodynamic test. The effects of the co-deposited particles on corrosion behavior of the coatings in 1.0 N H₂SO₄ and 3% NaCl media were investigated. The surface autocatalytic properties and the post-heat-treatment on coating corrosion resistance were also discussed. The results showed that both EN and EN composite coatings demonstrated significant improvement of corrosion resistance in both acidic and salty atmosphere. Ni striking substantially enhanced the corrosion resistance due to the improvement of the surface autocatalytic properties and homogeneity. Proper post-heat-treatment significantly improves the coating density and structure, giving rise to enhanced corrosion resistance.     

Black nickel electrodeposition from a modified Watts bath

Black nickel coatings were electrodeposited on to steel substrates from a Watts bath containing potassium nitrate. The best operating conditions necessary to produce smooth and highly adherent black nickel were found to be NiSO₄ · 6H₂O 0.63 M, NiCl₂ · 6H₂O 0.09 M, H₃BO₃ 0.3 M and KNO₃ 0.2 M at pH of 4.6, i=0.5 A dm⁻², T=25 °C and t=10 min. The modified Watts bath has a throwing power (TP) of 61%, which is higher than that reported, not only for nickel, but also for many other metals electrodeposited from different baths. The potentiostatic current–time transients indicate instantaneous nucleation. X-ray diffraction (XRD) analysis shows that the black nickel deposit is pure metallic nickel with Ni(111) preferred orientation.     

变形锌合金在柠檬酸盐镀镍液中的腐蚀行为

利用动电位极化曲线和电化学阻抗谱研究了变形锌合金在柠檬酸盐电镀镍溶液中的腐蚀行为,通过场发射扫描电镜(SEM–EDS)表征了腐蚀表面形貌和成分。结果表明,锌合金在镀液中呈活性溶解状态,柠檬酸钠对锌合金有缓蚀作用;提高镀液温度不仅加剧锌合金腐蚀,还会加快镍置换反应发生。     

化学镀镍槽热损失的最小化

在不使用电能的情况下,化学镀依靠含有还原剂的水溶液中金属离子的催化还原,从而实现金属的沉积.其成功与否,很大程度上取决于温度的维护.温度升高,沉积速度加快,因此,应当避免热量散失到周围环境中.本丈估算了包裹不同隔热材料的化学镀镍液的散热量.结果表明,采用棉花作为隔热材料,热损失可降至最低,从而提高并维持一定的沉积速率.     

Hierarchically porous-structured nickel oxide film prepared by chemical bath deposition through polystyrene spheres template

We report a facile and effective approach for the fabrication of hierarchically porous-structured NiO film. In this approach, the NiO film was deposited by chemical bath deposition through a self-assembled monolayer of polystyrene spheres template. The obtained NiO film exhibits a special hierarchical structure consists of two parts: the lower part is nickel oxide monolayer hollow-sphere array and the upper part is randomly porous net-like nickel oxide. The as-prepared NiO also shows a high specific surface area of 537 m² g⁻¹ and a narrow pore distribution centered at 140 nm. This is a technique for preparing large area hierarchical porous oxide or hydroxide films, which have a great promise for applications in optical devices, electrochemical sensors and thin-film batteries.     

Establishing relationships between bath chemistry, electrodeposition and microstructure of Co-W alloy coatings produced from a gluconate bath

Electrodeposited Fe group: W and Mo alloys have the potential to replace hard Cr coatings for use in engineering applications where wear and corrosion resistance are needed. Electrochemical studies have concentrated in the past on Ni-W alloy deposition, but now interest in Co-W alloys has developed as they possess lower coefficients of friction when in contact with another metal. The most attractive coating composition is in the range 14-20 at.% W, if controlled deposition promotes crystalline alloys of high hardness, rather than softer amorphous alloys containing >20 at.% W. This paper employs ammonia free baths with low concentrations of cobalt and sodium tungstate and varying additions of sodium gluconate to produce alloys at close to 50% efficiency. Voltammetry, UV and visible spectrometry, and potentiostatic deposition have been performed on such baths, whilst XRD, SEM and TEM observations have been made on the deposits. This aims to optimise the process and to understanding the relationships between bath contents, electrochemical kinetics and alloy composition. Efficient deposition of coatings with hardness values up to 1000 kgf mm⁻² occurred from a bath containing a high concentration of gluconate. Such deposits arise from concentrations of Co-W-gluconate complexes which promote the formation of nanoscale alloy grains. Current densities up to 2.75 A dm⁻² in the agitated bath promoted deposition kinetics to form these highly orientated structures. These kinetics produced nano-segregation of W which may be assisted by the migration of Co-W clusters to boundary sites during the growth of the deposit.     

Properties and microstructure of nickel electrodeposited from a sulfamate bath containing ammonium ions

A 70 m thick Ni layer was electrodeposited from a sulfamate bath containing various amounts of ammonium ions onto a copper plate. The detailed microstructure of the Ni deposits was characterized using a plane-view and cross-sectional transmission electron microscopy (TEM). The textures of the Ni deposits were also determined using conventional X-ray diffraction. Experimental results indicated that ammonium ions suppressed the lateral growth of Ni deposits and favoured out growth, thus leading to the growth of [1 1 0] and [3 1 0] oriented deposits. A structural refinement effect was observed after ammonium ions were added to the sulfamate bath. Ammonium ions also increased the internal stress and hardness of the deposits. A general Hall–Petch relationship was observed for the dependence of deposit hardness on the average grain size of the Ni deposits. The adsorption of atomic hydrogen and the polar NH₃ molecule explains the effect of ammonium ions on the electrocrystallization of Ni.     

Electrodeposition of zinc-nickel alloy coatings from a chloride bath containing NH4Cl

Zinc-nickel alloys were electrodeposited on steel from chloride baths containing NH₄Cl using different plating conditions. Current density, temperature and nickel percentage in the baths were found to strongly influence the composition of the deposits and the morphology. At low current densities transition from anomalous to normal codeposition was observed. The changes in potential, current efficiency, composition and morphology which follow the transition were studied. No increase in the partial current of hydrogen reduction was observed at the potential values from which anomalous codeposition begins; this fact, plus the formation of zinc ammonium complexes, seems to exclude the precipitation of zinc hydroxide at the electrode surface. The electrodeposition of zinc-nickel alloys is discussed emphasizing the importance of kinetic parameters and cathodic potentials.     

Electrodeposition of cobalt-nickel alloys from Watts-type baths

The electrodeposition of cobalt-nickel alloys was carried out from Watts-type baths of composition 5–60gl⁻¹ CoSO₄ · 7H₂O, 100–300gl⁻¹ NiCl₂ · 6H₂O and 25gl⁻¹ H₃BO₃ at a pH of 4.4. The cathodic polarization during electrodeposition and the alloy composition were greatly influenced by the concentrations of the depositable metal ions; whereas, the cathodic efficiency was only slightly affected. Under the examined conditions, the electrodeposition of the alloys belonged to the anomalous type. X-ray diffraction studies revealed that the alloys were deposited in the face-centred cubic structure and consisted of a mixture of the two phases α(Co) andβ(Ni). Sound, smooth and bright alloy deposits were obtained and their properties were improved by increasing the nickel content of the bath.     

柠檬酸盐体系低温化学镀镍的研究

提出一种柠檬酸三铵体系的低温化学镀镍工艺。研究了该镀液的温度、pH及镀液组成对沉积速度的影响。得出适宜的工艺条件为:40g/L硫酸镍、35g/L次亚磷酸钠、30g/L柠檬酸三铵,pH9~9.5,θ为45℃。经扫描电子显微镜观察,镀层表面均匀平整;经X-射线衍射分析,镀层具有晶态结构。该工艺稳定,沉积速度可达4.5mg/(cm2·h)。     

Codeposition of SiC powders with nickel in a Watts bath

The effect of the silica layer of SiC powder on ionic adsorption was studied in a Watts nickel plating bath. PZC (point of zero charge) measurement suggested that SiC powder has a tendency to release H⁺ at pH > PZC ( 2.2), and the amount of Ni²⁺ adsorbed on the surface of the SiC increased with increased pH of the Watts bath. Experimental results showed that SiC powders not only catalyzed the adsorption of hydrogen atoms but also had a significant effect on hydrogen evolution during electrodeposition if the solution pH was less than or equal to 2.0 (PZC. Furthermore, SiC powders have a shielding effect which prevents OH^– from being released into the solution under an applied potential, which results in more Ni(OH)₂ in the deposited layer. SiC powders also promote further adsorption of intermediates of nickel on the electrode surface, as shown by impedance studies.     

EDTA络合滴定法测定镀镍溶液中的镍含量

以5-Br-DMPAP作为指示剂,采用EDTA络合滴定法测定镀镍溶液中的镍含量。阐述了该方法的原理分析步骤,探讨了指示剂的选择对测量结果的影响,分析了干扰元素的影响及消除。测试结果表明,该方法用于镀镍液的测量,相对误差为0.27%,能满足实际生产的要求。     

Influence of additives on the electrodeposition of nickel from a Watts bath: a cyclic voltammetric study

The electrochemical reactions occurring during the deposition of nickel from a Watts bath have been examined using a voltammetric technique. The important reactions taking place at the anode and cathode have been systematically identified. The influence of the additives on the cathodic and anodic reactions show the importance of careful bath preparation for a quality controlled product. From the surface coverage data, the free energy change (G _a ⁰ ) for the adsorption of the brighteners has been calculated and compared with results from methods used earlier.     

Electrodeposition of ternary nickel—iron—cobalt alloys from acetate bath

Ternary nickel—iron—cobalt alloys of wide range composition have been deposited from acetate baths under a variety of conditions and the optimum conditions established are: nickel acetate 0.2828 M, ferrous sulphate 0.0359 M, cobalt acetate 0.2828 M, boric acid 0.1617 M, ascorbic acid 0.0056 M, pH 5.0, cd 1.5 A/dm² and temperature 30°. The bath gave bright, smooth and adherent deposits. Iron and cobalt contents decreased with an increase in cd and pH, X-ray studies of the deposits revealed fcc structure within the composition range studied (43.6–54.0% Ni). The results indicate that acetate bath can be successfully employed for plating purposes.