Showing papers on "Salt spray test published in 2006"

Corrosion protection for aerospace aluminum alloys by Modified Self-assembled NAnophase Particle (MSNAP) sol–gel

Abstract: The Air Force Research Laboratory is developing environmentally benign alternatives to the traditional chromated aircraft coating for aircraft corrosion protection, targeted at a 30+ year performance life cycle. The Self-assembled NAnophase Particles (SNAP) process is a new method of forming functionalized silica nanoparticles in-situ from hydrolyzed tetramethoxysilane (TMOS) and glycidoxypropyltrimethoxysilane (GPTMS) in an aqueous sol–gel process, and then cross-linking the nanoparticles to form a thin, fully dense, protective film on Al aerospace alloys. These nanostructured coatings have been shown to provide an excellent barrier to corrosion for aluminum aerospace alloys; and other applications are envisioned. Much work has been done on characterization and performance of these coatings. This paper discusses a modification of SNAP formulation with tetraethoxysilane (TEOS). Films were formulated and developed to produce a dense barrier sol–gel coating on AA2024-T3. Corrosion protection properties of the films were evaluated with potentiodynamic scan (PDS) electrochemical technique, electrochemical impedance spectroscopy (EIS) and Salt Spray test (5% NaCl).

Electrodeposition of zinc–nickel compositionally modulated multilayer coatings and their corrosion behaviours

Abstract: Zinc–nickel compositionally modulated multilayer (CMM) coatings were produced by successive deposition from dual baths containing a zinc sulphate electrolyte and a nickel–ammonia complexed electrolyte. The surface and cross-sectional morphologies of zinc–nickel CMM samples were examined using scanning electron microscopy (SEM). Corrosion resistance evaluated by means of neutral salt spray test showed that zinc–nickel CMM coatings were more corrosion-resistant than the monolithic coating of zinc or nickel of similar thickness. Result obtained from corrosion potential measurement and anodic polarisation suggest that pores and perhaps microcracks existed in nickel sublayer, which played an important role in achieving improved corrosion resistance for zinc–nickel CMM coatings. Based on results from electrochemical measurement and the micrographic characteristics of zinc–nickel CMM coatings after corrosion testing, a probable corrosion mechanism of zinc–nickel CMM coatings was proposed.

Electrochemically synthesized polypyrrole films as primer for protective coatings on carbon steel

Abstract: The use of electrochemically synthesized polypyrrole (a conducting polymer) film is investigated as a primer for protective coating on carbon steel. It provides excellent adherence and corrosion resistance, and is more environment-friendly. Polypyrrole was galvanostatically synthesized on carbon steel, and epoxy paint top coat was applied on it. The corrosion performance was evaluated using salt spray test, Tafel plots, and electrochemical impedance spectroscopy. The performance was compared to that of a commercial zinc primer. These tests coherently demonstrate that the use of polypyrrole film inhibits corrosion better than a zinc primer in salt and acid environments.

Surface Modification With Zinc and Zn-Ni Alloy Compositionally Modulated Multilayer Coatings

Abstract: Zinc and Zn-Ni alloy compositionally modulated multilayer (CMM) coatings were electrodeposited on to a steel substrate by the successive deposition of zinc and Zn-Ni alloy sublayers from dual baths. The coated samples were evaluated in terms of the surface appearance, surface and cross-sectional morphologies, as well as corrosion resistance. The microstructural characteristics that were examined using the field emission gun scanning electron microscopy (FEGSEM) confirmed the layered structure, grain refinement of the zinc and Zn-Ni alloy CMM coatings, and revealed the existence of microcracks caused by the internal stress in the thick Zn-Ni alloy sublayers. The corrosion resistance that was evaluated by means of the salt spray test shows that the zinc and Zn-Ni alloy CMM coatings were more corrosion-resistant than the monolithic coatings of zinc or Zn-Ni alloy of the same thickness. The possible reasons for the better protective performance of Zn-Ni/Zn CMM coatings were given on the basis of the analysis on the micrographic features of zinc and Zn-Ni alloy CMM coatings after the corrosion test. A probable corrosion mechanism of zinc and Zn-Ni alloy CMM coatings was also proposed.

Effect of Ce surface treatments on corrosion resistance of A3xx.x/SiCp composites in salt fog

Abstract: The influence of the SiCp proportion and the matrix concentration of four aluminum metal matrix composites (A360/SiC/10p, A360/SiC/20p, A380/SiC/10p, A380/SiC/20p) modified by cerium-based conversion or electrolysis coating was evaluated in a neutral salt fog according to ASTM B 117. Cerium-based conversion coatings obtained by immersion in 50 °C solution of Ce(III) salt and cerium electrolysis treatment carried out in ethylene glycol mono-butyl ether solution preferentially covered the intermetallic compounds and SiCp. The kinetics of the corrosion process was studied on the basis of gravimetric tests. Both the coating microstructure and the nature of corrosion products were analyzed by SEM, EDS and low angle XRD before and after accelerated testing to determine the influence of microstructural changes on corrosion behavior during exposure to the corrosive environment. The corrosion process was influenced more by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement. Both cerium treated surfaces presented better behavior to salt fog corrosion than original composite surfaces without treatment; however, electrolysis afforded a higher degree of protection than the conversion treatment because the coating was more extensive.

Corrosion behavior of wire-arc-sprayed stainless steel coating on mild steel

Abstract: The corrosion characteristics of a wire-are-sprayed stainless steel coating on mild steel have been investigated in regards to atomizing gases and sealing treatment. Salt spray test was performed. The corrosion behavior of the coating was observed under a microscope succesively through a cycling test of wetting and drying in a salt solution. The sealing-treated coating was found to rust faster compared with the non-sealing-treated coating; it protected the mild steel substrate against corrosion, but even it deteriorated the coating itself due to the interruption of the substrate as an anode. The air-atomized coating ruste more heavily than the nitrogen-atomized one. Four different phases were observed in the coating in regards to corrosion behavior; namely, chromium-based oxide, iron-based oxide, chromium-depleted metallic phase, and stainless steel matrix phase. It was found that the chromium-depleted metallic phase and the iron-based oxide are non-corrosion-resistant, whereas the chromium-based oxide and the stainless steel matrix phase are corrosion-resistant.

Corrosion of Sn-Ag-Cu lead-free solders and the corresponding effects on board level solder joint reliability

Abstract: The drive for lead-free solders in the microelectronics industry presents some new reliability challenges. Sn-Ag-Cu alloys are leading candidates for lead-free solders. Compared to traditional Sn-Pb solders, Sn-Ag-Cu solders are easily corroded in corrosive environment due to their special structure. The presence of Ag/sub 3/Sn in Sn-Ag-Cu solders accelerates the dissolution of tin from solder matrix into corrosive medium because of galvanic corrosion mechanism. When the corrosion present in the solder joints, it may change the microstructure of corroded regions and decreases the mechanical properties of solder joints by providing a crack initialization. In the present paper, the effects of salt spray test (based on JESD22-A107B) on the microstructure and mechanical properties of Sn-4.0%Ag-0.5%Cu solder balls are investigated with shear and ball pull test. The results show that the shear and pull strength of lead-free solder balls decreased after the slat spray test. In addition, three kinds of tests are performed to evaluate the effects of corrosion on the board level reliability of Sn-Ag-Cu solder joints, including drop test, three-point single strike and cyclic bending.

Corrosion behaviour of galvannealed steel sheet

Abstract: This paper analyzes the influence of galvannealed coating on the corrosion behaviour of press-formed and painted galvannealed steel sheet (GA) against the painted cold rolled and closed annealed (CRCA) sheet evaluated by electro impedance spectroscopy (EIS), salt spray (SST) and combined cyclic corrosion test (CCT). EIS study showed a significant decrease in the polarization resistance from 6.38 to 0.8 Ω/cm 2 in case of CRCA painted sheet and from 6.07 to 4.07 Ω/cm 2 in case of GA painted material revealing the superior corrosion resistance of galvannealed sheet. This was also confirmed from the scribed samples exposed to salt spray test. The corrosion product was also very low in GA painted compared to CRCA at scribed areas. Studies on under-paint corrosion from a deep scratch or creep-from-scribe in combined cyclic corrosion tests (CCT), simulating drying and wetting conditions in actual service life, have shown drastic reduction in creep-back for GA material. Salt spray test (SST) exposure of 720 h on painted and cross-scribed samples has also demonstrated the ability of GA material to resist corrosion that inevitably occurs on stone chipping on outer surface of auto body panels. Red rust formation started just after two cycles and propagated from crosscut portion with further test cycles. The initiation of red rust across the crosscut in GA material was not visible even after 65 cycles. The corrosion rates of CRCA painted samples after 30 and 45 cycles were 5.17 and 11.56 mpy, respectively, while in the case of GA painted, it was only 0.412 and 0.732 mpy, respectively. In case of CRCA, the corrosion rate increased with the passage of time. After 45 cycles of testing, GA painted sample has shown almost 16 times more corrosion resistance than the painted CRCA material.

Element of arc oxidation electrolyte of corrosion resistant magnesium alloy, and method of element of arc oxidation

Abstract: This invention relates to a corrosion resisting magnesium alloy micro-arc oxidation electrolyte and its micro-arc oxidation method. The electrolyte contains 5~25g/L phytic acid or its alkali metal salt, 5~40g/L hydrofluoric acid or its ammonium salt, 15~70g/L phosphoric acid or its ammonium salt, 5~60g/L boracic acid or its ammonium salt (and/or fluoboric acid or its ammonium salt). The process includes following steps: a) preprocessing, including grinding, degreasing and pickling. b) micro-arc oxidation. Hydrofluoric acid, phosphoric acid and boracic acid/fluoboric acid or their ammonium salts are added into phytic acid (or its alkali metal salt) solution, which is subsequently adjusted to a pH value of 6~10 with one or several species among ammonia, hexamethylene tetramine and diethylene triamine and then oxidized. c) Postprocessing. The micro-arc oxidation electrolyte adopted in this invention is free of Cr6+ and thus brings little pollution to the environment. The films obtained are smooth on the surface with only small-scale pores and have ceramic appearances. The oxidized samples without any postprocessing undergo a 5% NaCl neutral salt spray test and evaluated 8-class according to Criteria ASTM B537-70.

Mg2Si Coating Technology on Magnesium Alloys to Improve Corrosion and Wear Resistance

Abstract: Magnesium silicide (Mg 2 Si) bulky materials are useful to improve the surface function of light metals such as magnesium or aluminum alloys, due to its superior corrosion resistance to the conventional stainless steel, and its high mechanical properties. In this study, Mg 2 Si thin film coated on AZ31 magnesium alloys by using a high frequency sputtering method, was examined. A neutral salt spray test to evaluate the corrosion resistance indicated that AZ31 substrate with Mg 2 Si coating was hardly damaged after 240 h. On the other hand, the non-treated one was corroded in only 1 h. Concerning wear resistance under the oil lubricant test, a friction coefficient of the AZ31 alloy with Mg 2 Si film is remarkably stable in employing S35C steel as a counter specimen. No sticking between both specimens was detected. In the combination of AZ31 alloy disc and S35C pin specimens, seizure and sticking phenomena occurred and the μ value suddenly increased. Accordingly, Mg 2 Si coating technology is a suitable surface modification process to improve corrosion and wear resistance of magnesium alloys.

Chromium-free rust inhibitive treatment method for metal products having zinc surface and metal products treated thereby

Abstract: Provided is a chromium-free surface treatment method which imparts practical rust inhibitive performance to a metal product having a zinc surface to which it was difficult to impart rust inhibitive performance of practical level. A conversion-coated film of zinc phosphate etc. is formed on the zinc surface of the metal product as pretreatment, and the silica-based film is formed by applying a chromium-free surface treatment agent which uses alcohol or mixture of water and alcohol as a solvent to the conversion-coated film. As a result, when an aqueous surface treatment agent containing alcohol is applied, it is possible to suppress the formation of white rusting for 72 hours or longer in the salt spray test.

Optimization of Environmentally Friendly Anodic Oxide Film for Magnesium Alloys

Abstract: The magnesium anodizing treatment described in this paper is an environmentally friendly treatment which excludes the use of chromates, fluorine compounds, and phosphates. An alkali bath, which mimics conditions necessary to form naturally occurring magnesium salts, was selected as an electrolytic bath. The components of the electrolytic bath were optimized, and the samples were evaluated by salt spray test. The results suggest that the anodizing treatment with the optimized conditions on the surface of magnesium alloys AZ91 can achieve a higher level of corrosion resistance than the traditional chemical conversion and anodizing treatments which use chromates, fluorine compounds, and phosphates.

배기계용 고내식 알루미늄 도금강판의 부식특성에 관한 연구

Abstract: Effect of Cu₂S for improvement in corrosion resistance of highly corrosion-resistant aluminized steel sheet was investigated by means of corrosion test and heat-corrosion resistance test. For the test similar to actual driving conditions, test was carried out by the following methods which are chipping test at room temperature and salt spray test for 1300 hours after heating the specimen for 24 hours at 400, 500, and 600℃. And also, after cycle corrosion test, maximum pit depth measurement was executed for testing of heat-corrosion resistance for highly corrosion-resistant aluminized steel sheet. The contents variation of between coating surface and substrate was measured by GDS. Effect of Cu₂S for improvement in corrosion resistance was verified by the test above.

QPQ Salt Bath Nitriding and Corrosion Resistance

Abstract: The QPQ complex salt bath treatment is a type of surface strengthening technology which contains mainly salt bath nitriding and salt bath post-oxidizing processes. The effect of nitriding temperature and duration on the corrosion resistance of QPQ treated specimens is explored by immersion tests and salt spray tests in this paper. The material used in this study was 1020 annealed steel. In the immersion tests, the specimens were immersed in 3‰H2O2 and 10% NaCl water solution. In the salt spray tests, specimens were salt spray tested using a 5% NaCl neutral solution. The data indicate that, when the nitriding duration is less than 2 hours at temperature below 590
(phase change will exist when the nitriding temperature is above 590
according to Fe-N phase diagram) , the higher temperature of the salt bath nitriding , the specimens will have the higher corrosion resistance. In addition we have found that nitriding for too short a time generates a thin compound layer, and nitriding for too long generates too much porosity. Both will deteriorate the corrosion resistance.

Corrosion Behavior during Cyclic Salt Spray Test of Friction Stir Welded A7075 and A6N01 Aluminum Alloys

Abstract: A cyclic neutral-salt spray test, CCT, has been applied to friction-stir-welded A7075 and A6N01 aluminum alloys and corrosion behavior in each region of stirred-zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM) in the joints are studied. Weight loss, appearance of corroded regions, depth of corrosion and so forth were examined by means of optical and scanning electron microscopies and violet laser color 3D profile microscope. Energy dispersive X ray spectroscopy, EDS, analysis was made on SZ, TMAZ, HAZ and BM regions of the joints. It was found that the region of the TMAZ/HAZ boundary and around it was most susceptible to corrosion among the four regions in both of the FSWed A7075-T6 and A7075-O alloys. The EDS result showed that Cu might be enriched in the TMAZ/HAZ region. It seemed that a main cause of the susceptibility to corrosion in the TMAZ/HAZ region was due to the formation of the second phase particles containing Cu in them in the region. We presumed that the Cu atoms migrated from SZ to TMAZ/HAZ during FSW process that brought about sharp temperature and internal stress gradient in the alloy, which would lead to the enrichment of Cu in the TMAZ/HAZ region. Meanwhile, the FSWed A6N01-T5 alloy showed excellent corrosion resistance under CCT for 1000 h.

Micro-arc Oxidation of AZ91 Die Cast Magnesium Alloys in Phosphate Electrolyte

Abstract: A series of micro-arc oxidation (MAO) layers were produced on AZ91 die cast magne- sium alloys in phosphate electrolyte with different parameters. The effects of concentration of sodium phosphate and sodium hydroxide, current density and duration on MAO layers growth regularity were discussed. The surface features and corrosion resistance of the layers were investigated using scan- ning electron microscopy and neutral salt spray test, respectively. The results show that the corrosion resistance of AZ91 die cast magnesium alloy improved greatly after MAO treatment. The optimum technological condition was settled as follows: 5 g·l-1 Na3PO4, 6 g·l-1 NaOH, 3 A·dm-2 current density and 10 min duration, in which the sample oxidized had a beneficial surface morphology and corrosion rate of 0.132 6 mm/a.

Influence of Pretreatment on Cerium Conversion Coatings of Aluminum Alloys

Abstract: With the certain deposition process, the conversion coatings by four different pretreatments on LF21 were studied. The morphology and the chemical composition of the conversion coatings were examined by scanning electron microscopy (SEM). The corrosion resistance was investigated by electrochemical impedance spectroscopy (EIS) and the salt spray test. The results showed that the different pretreatments had obvious effect on the cerium conversion coatings. For the certain deposition process, the optimal pretreatment process was identified.

A Novel Anti-Corrosion Coating for Aluminium Alloy

Abstract: A novel environmental protective water based metallic coating was developed for aluminum alloys, which mainly contains metal flake, silicate and silane. The coating's properties were investigated by neutral salt spray test, micro-hardness testing, adhesion test and electrochemical technique etc. Meanwhile the coating's surface and microstructure was observed by scanning electron microscopy (SEM). Furthermore, the film forming matter was examined by Fourier transform infrared spectroscopy (FTIR) test. Results showed that an excellent adhesive, heat-resisting, protective coating for aluminum alloy could be achieved by this technique. An interpenetrating polymer network (IPN) was formed in the coating by means of cross linking reaction of organosilicone and inorganic silicate. In thesis, the film forming mechanism and protection of coating were also discussed.

Study on Corrosion Resistance of Micro-Arc Oxidation Ceramic Coating of High Strength Casting Aluminum Alloy

Abstract: The influence of thickness of micro-arc oxidation( MAO) coatings on the corrosion resistance of high strength casting aluminum alloy ZL205 was investigated by using salt spray test It was found that MAO coatings improved the corrosion resistance of ZL205 alloy obviously The corrosion resistance of MAO coatings increased with the increase of coating thickness When the coating thickness was thicker than 30μm, the corrosion resistance of PEO coating increased only a little with the increase of PEO coating thickness Results of SEM and XRD showed that surface morphologies and phase composition of MAO coatings altered with the increase of oxidation time, which resulted in different corrosion resistance of MAO coating

Organic coated steel sheet excellent in edge creep resistance

Abstract: PROBLEM TO BE SOLVED: To provide an organic coated steel sheet excellent in edge creep resistance SOLUTION: The organic coated steel sheet is constituted by providing an organic coating layer on a steel sheet having a Zn-plated layer containing at least Al and Mg When a salt spray test based on JIS Z 2371 is applied to the organic coated steel sheet, a corrosion product containing at least Mg, Al and Zn is formed on one side or both sides of the cut end surface part or organic coating surface of the organic coated steel sheet and the mass ratios of Zn and Al as well as Zn and Mg in the corrosion product are respectively 3≤Zn/Al≤15 and 10≤Zn/Mg≤30 COPYRIGHT: (C)2006,JPO&NCIPI

Corrosion Resistance of Magnesium Alloy with Complex Surface-Modifying Micro-Arc Oxidation Coating and Organic Coating Studied by Neutral Salt Spraying

Abstract: Magnesium alloy AZ91D was surface-modified by micro-arc oxidation (MAO). Several organic coatings were then prepared on the micro-arc oxidation coating of the Mg alloy. The corrosion resistance of the dual-phase surface-modification coatings was evaluated using neutral salt spray test. It was found that the micro-arc oxidation coating in combination with organic coatings contributed to significantly increase the corrosion resistance of the Mg alloy, which could make it possible for the Mg alloy after the dualphase surface-modification to be used in severely corrosive working conditions. Specifically, the micro-arc oxidation coating combined with electrophoresis coating was the most effective in increasing the corrosion resistance of the Mg alloy. The reason could lie in that the micro-arc oxidation coating was able to refine the surface microstructure of the Mg alloy and hence considerably increase the adhesion strength of the organic coatings thereon.

Research on water based coating containing nano-silica for magnesium alloy

Abstract: Due to magnesium's active chemical property, a novel environmental protective water based metallic coating was developed, which mainly contains metal flake, nano-silica, silicate and silane. The coating's properties were investigated by neutral salt spray test, micro-hardness testing, adhesion test and electrochemical technique etc. Meanwhile the coating surface and microstructure was observed by scanning electron microscopy (SEM). Furthermore, the effect of nano silica on the coating was also explored. Results showed that an excellent adhesive, heat-resisting, protective coating for AZ91D magnesium alloy could be achieved by this technique. It also indicated that nano silica could greatly improve the properties of coating. In the paper, mechanism of nano silica coating was also discussed.

Study on the mechanical properties and corrosion resistance properties of nanometer barite /epoxy composite paint film material

Abstract: The modification of nanometer barite and effect of dosage of nanometer barite on the hardness,T-bending performance,the strain,and salt spray test of the paint films have been investigated in detail.The fractured surface of nanometer barite/epoxy composite paint films and the disperse characters of stuffing were observed by SEM images.The results indicated that nanometer barite modified with 5% sodium stearate possessed the biggest activation indices,and better dispersibility.The performances of composite paint film adding 1.0% modified nanometer barite were improved largely,the T-bending was improved from 4T to 2T,and the corrosion resistance increased 20% with its retardation time from 720～1096h before showing blisters.Moreover,nanometer particles dispersed uniformly in the paint film was characterized by SEM images.