Search results

Potassium silicate sealer was applied on solvent-cleaned, acid-pickled, dacromet-coated steel to improve its corrosion resistance. The purpose of this paper is to study the corrosion behavior of dacromet-coated steel.

Potassium silicate sealer was applied on solvent-cleaned, acid-pickled, dacromet-coated steel to improve its corrosion resistance. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and salt spray were carried out. SEM was used to study the morphological appearance of the surface.

The EIS behavior indicated that solvent-cleaned dacromet-coated steel sealed with potassium silicate showed that the corrosion current density was 2.664E − 5 A.cm² which was reduced to 8.752E − 6 A.cm² and the corrosion rate, which was 2.264E − 2 mm.year⁻¹, was reduced to 7.438E − 3 mm.year⁻¹ in NaCl 3.5 wt.per cent. EIS was used in NaCl 3.5 wt.%, and the Bode plot characteristics showed that the corrosion protection of solvent-cleaned, dacromet-coated steel was enhanced when sealed with potassium silicate. The EDS results of salt-sprayed, solvent-cleaned samples after 10 days indicated that the main corrosion products are composed of SiO₂, ZnO and Al₂O₃.

The detection of Li element in EDS was not possible because of the device limitation.

The current paper provides new information about the sealing properties of potassium silicate and its effects on the corrosion resistance of dacromet coating, which is widely used in many industries such as the automobile industry.

This study aims to investigate the salt spray corrosion (SSC) and electrochemical corrosion of obtained Zn–Al coating, which provided a basis for comprehensive analysis of corrosion behavior of Zn–Al coating.

A Zn–Al coating was fabricated on Q235A steel using a Dacromet method. The SSC and electrochemical corrosion performances in 3.5 Wt.% NaCl solution were investigated using an SSC chamber and electrochemical workstation, respectively, and the corrosion mechanism of Zn–Al coating was discussed.

The Dacromet fabricated Zn–Al coating is primarily composed of Zn and Al phases, its residual stress of −11.1 ± 4 MPa is compressive stress, which is beneficial to improve its corrosion resistance. In the SSC process, the corrosion product of Zn5(OH)8Cl2H2O enhances the corrosion resistance of Zn–Al coating, which provides sufficient cathodic protection for the substrate. The corrosion potential of Zn–Al coating is lower than that of substrate, which provides sufficient cathodic protection to the substrate, the Zn–Al coating in the immersion periods is protected by the corrosion product and Zn–Al sheets.

In this study, a Zn–Al coating was first fabricated on Q235A steel using a Dacromet method.

ACEL — Tay Bridge cathodic protection. Aberdeen Corrosion Engineers Ltd in conjunction with R B R (Scotland) Limited, have been awarded a major contract for structural repairs and installation of cathodic protection to supporting columns of the River Tay A92 Road Bridge at Dundee. Work commenced during July 1989, and comprises installation of expanded titanium mesh using both sprayed and poured mortar overlays.

Protection against corrosion in the automotive industry Those with memories of motoring in pre‐war days, or even early post‐war, are fond of telling us how their cars did not corrode to the extent that ours do today. In the main, this is true. Not because of the reason they usually put forward, i.e. “we had at least six coats of good paint”, but because metal gauges have become progressively thinner in order to save weight; salting of roads in wintertime is a post‐war practice; and the higher speeds of today mean more damage to paint films by flying stones and gravel.

Spotlights the design and development of an aluminium chassis for the new Lotus Elise. Highlights the benefits of using aluminium extrusions and the reasons for choosing bonding as opposed to welding. Describes the assembly process and how the maintenance and repair drawback of a bonded design can be overcome. Notes that the largest proportion of Lotus’ sales actually come from engineering and consultancy services.

Heads up BCI's Metal Finishing Division. Brian Garner (47) has been appointed chairman of the Metal Finishing Division of Brent Chemicals International PLC. He is currently managing director of Pyrene Chemical Services, Britain's leading supplier of pretreatment chemicals and a major company within the Brent Chemicals International group. He joined Pyrene in 1976 as marketing director, becoming managing director in 1980.

The purpose of this paper is to examine the performance of a fastener composite coating system, sherardized (SD) coating/zinc-aluminum (ZA) coating whether it has good performance in marine environment.

In this paper, SD coating was fabricated on fastener surface by solid-diffusion method. ZA coating was fabricated by thermal sintering method. Corrosion behaviours of the composite coating were investigated with potentiodynamic polarization curves, open circuit potential and electrochemical impedance spectroscopy methods.

Neutral salt spray (NSS) and deep sea exposure tests revealed that the composite coating had excellent corrosion resistance. Polarization curve tests showed that corrosion current density of the sample with composite coating was significantly decreased, indicating an effective corrosion protection of the composite coating. OCP measurement of the sample in NaCl solution demonstrated that the composite coating had the best cathodic protection effect. The good corrosion resistance of the composite coating was obtained by the synergy of SD and ZA coating.

SD/ZA coating can be used in marine environment to prolong the life of carbon steel fastener.

SD/ZA composite coating can reduce the risk and accident caused by failed fastener, avoid huge economic losses.

A new kind of composite coating was explored to protect the carbon steel fastener in marine environment. And the composite coating has the long-term anti-corrosion performance both in simulated and marine environment test.

This paper aims to study the corrosion behavior of molybdate conversion coatings on AZ31 magnesium alloy in NaCl solution.

The open circuit potential curves, anodic polarization curves, electrochemical impedance spectroscopy and immersion tests were used to study the corrosion behavior of molybdate conversion coatings on AZ31 magnesium alloy in NaCl solution.

The molybdate conversion coatings were homogeneous and uniform. The corrosion resistance of AZ31 magnesium alloy had been improved evidently through the molybdate conversion treatment.

The molybdate conversion coatings possess favorable feasibility in practice for the corrosion protection of AZ31 magnesium alloys in NaCl solution.

This paper aims to examine the performance of low-pressure cold-sprayed zinc–nickel (Zn-Ni) composites coating, i.e. whether it has the same performance as Zn-Ni alloy coating.

In this paper, Zn-Ni composites coatings containing four different nickel contents were prepared with commercial DYMET 413 low-pressure cold spraying system under the same parameters. Corrosion behaviors of four kinds of coatings were examined with potentiodynamic polarization curves and electrochemical impedance spectroscopy methods, combined with scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.

Corrosion behavior of Zn-Ni composites coating is similar to Zn-Ni alloy coating. In the early stages of immersion, the anodic dissolution of zinc happens, which results in the formation of a zinc hydroxide layer. With the continuous infiltration of chloride ion, zinc hydroxide will get converted to zinc oxide, basic zinc chloride and basic zinc carbonate. The presence of nickel in coatings can prevent zinc hydroxide from converting into zinc oxide.

Further research should be done on improving the deposition efficiency, as the deposition efficiency of low-pressure cold spray is lower than 30 per cent.

Low-pressure cold spray coating can be used in cyclic dry/wet conditions to prolong the life of a steel structure.

Low-pressure cold spray Zn-Ni coating is an environmentally friendly anticorrosion method which can be used as an alternative of hexavalent chromium passivation coating.

Zn-Ni composite coating can be deposited on steel directly by low-pressure cold spray by mechanically mixing the powders together. The composite coating also has the same long-term anticorrosion performance as Zn-Ni alloy coating.

The purpose of this paper is to study the effect of different concentrations of pretreatment solution of copper acetate (1, 5 and 10 g/L) on the deposition, growth and protection ability of zinc phosphate coating.

Zinc phosphate coatings were deposited on steel surface by immersion method. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to study the morphological evolution and chemical analysis of formed coatings. The electrochemical performance of the coatings was evaluated via potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and immersion test in an aerated 3.5% NaCl solution.

The results showed that the activation treatment accelerated the deposition of the phosphate coating and improved its surface coverage. A higher phosphate coating weight (7.35 g/m²) and more compact structure was obtained with pretreatment solution of 1 g/L copper acetate. Electrochemical results revealed that the protection ability of the phosphated substrates was markedly enhanced after the pretreatment, and the best corrosion protection was obtained with a concentration of 1 g/L copper acetate solution. The corrosion current density of phosphated substrate was reduced by 64.9% after activation treatment with 1 g/L copper acetate solution.

In this investigation, dense, stable and compact zinc phosphate layers with improved corrosion resistance were formed on a carbon steel surface after activation pretreatment with copper acetate solution prior to a phosphating step.