Topographical and surface chemical studies of chromate-phosphate pretreatment films on aluminium surfaces

Treverton, J. A.; Amor, Mariano Pérez; Bosland, A.

doi:10.1016/0010-938x(92)90180-b

Cited by 26 publications

(3 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Chemical conversion treatment in chromate (Ref 3-7) or chromate-phosphate (Ref [8][9][10][11] solutions has frequently been used to modify aluminum alloy surfaces in the past. However, chromate solutions have been widely associated with carcinogenesis ( Ref 12,13), and its removal as a waste is a problem.…”

Section: Introductionmentioning

confidence: 99%

Characterization of phosphate films on aluminum surfaces

Cheng

Ramamurthy

McIntyre

1997

J. of Materi Eng and Perform

View full text Add to dashboard Cite

A thin layer of phosphate conversion coating was formed on pure aluminum in a commercial zinc-manganese phosphating bath. A number of surface analytical techniques were used to characterize the phosphate thin films formed after immersion times ranging from 30 s to 10 rain. The coating contained mainly a crystalline structure with dispersed micrometer-scale cavities. The major constituents of the phosphate film were zinc, phosphorus, and oxygen; a small amount of manganese was also detected. Based on these results, a three-stage mechanism was proposed for the formation and the growth of phosphate conversion coatings on aluminum. Electrochemical impedance spectroscopy was used to evaluate the corrosion performance of phosphated and uncoated aluminum samples in 0.50 M Na2SO 4 and 0.10 M H2SO 4 solutions. Both types of samples exhibited a passive state in the neutral solution and general corrosion behavior in the acid solution.

show abstract

Section: Introductionmentioning

confidence: 99%

Characterization of phosphate films on aluminum surfaces

Cheng

Ramamurthy

McIntyre

1997

J. of Materi Eng and Perform

View full text Add to dashboard Cite

show abstract

“…Surface analysis techniques have revealed that the composition of the coatings depends on the nature of the chemical conversion bath. [1][2][3] It is now agreed that the coatings are amorphous 2,3 and that both Cr͑III͒ and Cr͑VI͒ species are incorporated into the films, with possible formation of a mixed Cr͑III͒-Cr͑VI͒ oxide as suggested by recent Raman spectroscopy analysis. 4,5 The mechanism of action of chromate in assuring the protection against pitting corrosion is still under debate.…”

mentioning

confidence: 99%

Structural Analysis and Photocurrent Spectroscopy of CCCs on 99.99% Aluminum

Quarto

Santamaria

Mallandrino

et al. 2003

J. Electrochem. Soc.

View full text Add to dashboard Cite

A characterization of chromate conversion coatings ͑CCCs͒ formed in the presence and in the absence of accelerator ͑ferro-ferricyanide redox couple͒ has been performed by various techniques ͑transmission electron microscopy, TEM, glow discharge optical emission spectrometry, GDOES, X-ray absorption near-end structure, XANES, and photon correlation spectroscopy͒. The results of a detailed investigation on morphological, compositional, and solid-state properties of freshly converted aluminum samples at different immersion times ͑30 s-90 min͒ are reported. The TEM and GDOES data suggest the presence of iron-cyanide species only in the external layer of CCC of nearly constant thickness. The XANES data suggest the presence of both Cr͑VI͒ and Cr͑III͒ species with a ratio Cr͑VI͒/Cr͑III͒ close to 1:2. This ratio remains constant with the conversion time and seems slightly affected by the composition of conversion solution. The photoelectrochemical study suggests an insulating or slightly p-type behavior for CCC layers. A bandgap value of about 2.55 eV has been estimated, regardless of the conversion solution, although some differences in the photocurrent spectra have been observed for coatings formed in the presence or absence of accelerator. The location of electronic energy levels of the Al/CCC/electrolyte interface has been derived which could account for the different kinetics of coating formation in the presence of accelerator. A large research effort has been devoted in the last years to the understanding of the exact nature of the chromate conversion coating ͑CCC͒ and its mechanism of protection against corrosion of aluminum metal and alloys.Surface analysis techniques have revealed that the composition of the coatings depends on the nature of the chemical conversion bath.1-3 It is now agreed that the coatings are amorphous 2,3 and that both Cr͑III͒ and Cr͑VI͒ species are incorporated into the films, with possible formation of a mixed Cr͑III͒-Cr͑VI͒ oxide as suggested by recent Raman spectroscopy analysis. 4,5 The mechanism of action of chromate in assuring the protection against pitting corrosion is still under debate. From this point of view a large interest exists in understanding the influence of aging on the protection action of CCCs. It has been shown that long-term or temperature aging acts on the mechanism of release of Cr͑VI͒ species so affecting the ''active protection'' of CCCs also called self-healing. In this frame different hypothesis have been suggested to explain the associated loss of corrosion protection.5-9 Among those, structural changes occurring into the CCC and related to dehydration were evidenced. 10As for the mechanism of formation and growth of CCCs only very few papers have addressed both the role of the redox couples, usually added to the commercial conversion bath to speed up the growth of the coating, and the mechanism of initial formation of CCCs during the conversion process. 3,4 Brown et al.3 suggested that on a very pure Al surface a uniform coating develops due to a mechanism o...

show abstract

“…3(b) for reference, which indicates the presence of Cr 2 O 3 on the surface of the NP structures. 16 In addition, a slight spectral weight is evident at the threshold of the WS Cr 2p 3/2 peak, which possibly originates from metallic Cr. Therefore, the oxide layer formed by the etching solution probably consists of both Al oxide and Cr 2 O 3 .…”

Section: Introductionmentioning

confidence: 99%

Effect of electric field concentration using nanopeak structures on the current–voltage characteristics of resistive switching memory

et al. 2014

View full text Add to dashboard Cite

An attempt to reduce the SET voltage and RESET current of resistive switching (RS) memory was made using a geometric array of nanopeak (NP) structures. Bottoms of anodic porous alumina were used to form the NP structures that act as guides for the formation of conductive filaments that effectively concentrate the electric field. Samples were fabricated with flat surfaces (FS) and with two types of NP structure with different NP pitch. The NP samples provided SET voltages less than 2 V with narrow distributions and the RESET current was lower than that with the FS sample.

show abstract

Topographical and surface chemical studies of chromate-phosphate pretreatment films on aluminium surfaces

Cited by 26 publications

References 19 publications

Characterization of phosphate films on aluminum surfaces

Characterization of phosphate films on aluminum surfaces

Structural Analysis and Photocurrent Spectroscopy of CCCs on 99.99% Aluminum

Effect of electric field concentration using nanopeak structures on the current–voltage characteristics of resistive switching memory

Contact Info

Product

Resources

About