This paper presents a novel pretreatment method required for aluminum alloy substrates prior to electroplating. An electrolytic jet containing coarse lumpy SiC particles is ejected on the substrate with a jet velocity of 16.5m/s for 60s. Jet electroplating is performed using the same electrolyte immediately after the pretreatment without water rinsing. With the inclined jet to the substrate pretreated at different collision angles, an optimum angle of 45° produces the highest level of adhesive strength for the deposition. The inclined jet pretreatment with a substrate rotation provides higher adhesive strength. However, it is difficult to explain the increase in adhesive strength through the surface area of the substrates as measured by the AFM. The amount of aluminum transferred to the deposits after the peeling test is found to increase linearly with an increase in the interfacial area between the deposits and the substrate derived from the two directional interfacial lengths that include hook-shaped segments. Hence, an increase in adhesive strength is primarily due to the increase in the real interfacial area with the formation of hook-shaped segments.
The structure of thin film which grows on metal surfaces under electrodeposition is studied using a kinetic Monte Carlo method. As a model of crystal growth from solution, we extended the solid-on-solid model so that lattice defects (vacancies) were allowed to form in the film, and performed the simulations for a two-dimensional square lattice model. We take into account adding atoms on and subtracting atoms from the surface, and the diffusion of adatoms on the surface. The growth rate is controlled by the difference in the chemical potential between the fluid and solid phases. The chemical potential μ corresponds to the overpotential in the electrodeposition. We performed the simulations for a given binding energy between atoms and for several values of μ at a constant temperature. It is shown that surface changes from monolayer to multilayer structures and point defects appear in the film as μ increases. For sufficiently large values of μ, the surface does not show a layer structure and large voids are observed as well as point defects. The formation process and the structure of defects are closely related to the surface structure.
The corrosion resistance of steel sheets continuously vapor-deposited with Al-Cr alloy and the crystal structure of the deposited layer were studied. Furthermore, investigation of the electrochemical corrosion behavior and an analysis on the morphology and the state of the corrosion products were conducted. Al-Cr alloy deposited steel sheets with Cr content of about 10wt% had superior corrosion resistance and revealed about eight times higher corrosion resistance in salt spray environments when compared to steel sheets vapor-deposited with pure Al. Increase of the corrosion potential and the pitting potential and improvement in the corrosion resistance of the deposited layer itself were confirmed with an increase of Cr content. It is considered that the drastic decrease in the corrosion resistance of Al-Cr alloy deposited steel sheets with Cr content of over 10wt% is caused by the reduction of the galvanic protection of the deposited layer to the steel sheet. The corrosion products mainly consist of dense bayerite (β-Al(OH)3) and do not contain Cr compounds. The corrosion behavior was also discussed in connection with the crystal structure.
Depth profiles of Na-atoms implanted in glass-like carbon (GLC, 1.5g/cm3) were measured using of SIMS and RBS, and the atomic density of the implanted layers was determined by comparing SIMS and RBS results. Na-ion implantation was carried out with doses ranging from 1×1015 to 1×1017ions/cm2 at an energy of 150keV. SIMS results show that the depth profiles in low dose conditions are Gaussian and those in medium dose conditions are Gaussian like distributions with a hump. In a high dose condition, the profile indicates Na enrichment at the surface and broadening. RBS results are almost the same as those of SIMS, and in the high dose Na enriched layers involve an oxygen mixture. Comparing the depth profiles of SIMS with RBS, results show that the atomic density of implanted layers increases from 1.5 to 2.0g/cm3.