Review of surface pretreatments for aluminium alloys

Critchlow, Gary W.; Brewis, D.M.

doi:10.1016/s0143-7496(96)00014-0

Cited by 298 publications

(138 citation statements)

References 50 publications

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“…Although a number of prebond treatments exist [12], there is still a lack of industrial confidence in the current chromate-free anodising and related processes proposed for adhesive bonding of aircraft structures. These processes are not generally regarded as performing to CAA standards.…”

Section: Introductionmentioning

confidence: 99%

Novel methods, incorporating pre- and post-anodising steps, for the replacement of the Bengough–Stuart chromic acid anodising process in structural bonding applications

Yendall

Critchlow

2009

International Journal of Adhesion and Adhesives

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The present investigation focuses on novel anodising processes which are being developed for the replacement of the hexavalent chromium containing 40/50V Bengough-Stuart process, with particular emphasis on their resultant performance in structurally bonded systems used in the demanding and harsh environments encountered on operational aircraft. An electrolytic phosphoric acid based deoxidiser (EPAD)has been studied in combination with a standard sulphuric acid anodise. It has been shown that the EPAD provides an open porous structure in order to enhance adhesion to the modified sulphuric acid anodised (SAA) surface. Additionally, a post anodising (PAD) treatment has been used to aid structural adhesion in combination with the SAA processes.2 As a control, the standard 40/50V Bengough-Stuart chromic acid anodising (CAA) has been used as a baseline performance indicator in adhesion tests.Single lap shear (SLS) and modified Boeing wedge tests were used to determine adhesion performance. SLS tests were used to determine initial, dry joint strengths whilst wedge test joints immersed in deionised water for up to 100 hours gave a measure of joint durability. Overall, excellent initial joint strengths and durability have been found with both EPAD plus SAA and PAD plus SAA processes suggesting that these environmentally benign treatments may be used as possible drop-in replacements for the currently used hexavalent chromium process. Electron microscopy has been used to investigate the topographical changes introduced to the surface by the various surface pretreatments under investigation to provide an explanation for the observed adhesion test results.

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Section: Introductionmentioning

confidence: 99%

Novel methods, incorporating pre- and post-anodising steps, for the replacement of the Bengough–Stuart chromic acid anodising process in structural bonding applications

Yendall

Critchlow

2009

International Journal of Adhesion and Adhesives

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“…To promote good adhesion to a subsequently applied polymer such as an adhesive, primer or paint layer three commonly used anodising processes are sulphuric acid anodising (SAA), phosphoric acid anodising (PAA) and chromic acid anodising (CAA) [16]. For most aerospace and other important structural applications the process of choice is normally CAA although PAA is also extensively used, particularly in the US where it is the subject of the Boeing specification BAC 5555.…”

Section: Anodising and Adhesionmentioning

confidence: 99%

Fatigue and fracture assessment of toxic metal replacement coatings for aerospace applications

Cree

Devlin

Critchlow

et al. 2010

Transactions of the IMF

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The use of corrosion resistant, and adhesion promoting films and coatings is established industrial practice for many fatigue sensitive components and structures. However, recent environmental legislation restricting the use of a range of toxic heavy metals and their derivative processes, such as chromic acid anodising (CAA), has meant that a number of new coatings systems and pretreatments are currently being developed to replace the traditional processes still in use. Typical of these new systems are the boric acid-sulphuric acid anodising (BSAA) process which can be modified to provide excellent adhesive bonding properties; the sulphuric acid anodising process, which includes an additional electrolytic phosphoric acid deoxidizing stage (EPAD) to produce a duplex oxide layer, and the recently patented ACDC sulphuric acid anodising process which produces a two layered oxide film which can be tailored to produce different porosity volume fractions within each layer. This communication reports the preliminary findings of a study carried out to assess the fatigue response of Al2618:T6 aluminium alloys to these new processes. In contrast to CAA anodising, the initial results indicate that the EPAD and ACDC processes do not appear to have a significant affect on fatigue.

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“…[17] Water then decreases the mechanical properties of adhesive (tensile strength and Young's modulus) [4][5][6][7][8][9], may (depending on surface treatment) cause corrosion in the substrate at the interface [18][19][20], and hydration of strong metal oxides [21,22]. The consequences of the diffused water in the adhesive joint are reductions in the joint strength, both static [23][24][25][26][27][28] and fatigue [29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

“…A good aluminium substrate surface preparation such as chromic acid etching (CAE), phosphoric acid anodizing (PAA) and priming gave excellent durability under static [9,22,33] and fatigue [21,29,32,34,] loading, with final failure within the adhesive layer even though the joints had been exposed in a hostile environment for long time.…”

Section: Introductionmentioning

confidence: 99%

The static and fatigue responses of aged metal laminate doublers joints under tension loading

Sugiman

Crocombe

2015

Journal of Adhesion Science and Technology

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Experimental studies have been undertaken to investigate the static and fatigue response of metal laminate doublers (MLD) joints under tension loading after ageing in deionised water at a temperature of 50 o C up to 2 years. It was found that absorbed water did not have a significant effect on the static and fatigue degradation of the MLD; however corrosion pits located on the aluminium surfaces caused a reduction in fatigue life.Inevitably the laminate contained butts where co-planar aluminium sheets were joined, and it was found that the position of the butt affected the static response of the MLD but, due to a restricted dataset, it has not been possible to assess the effect under fatigue loading. The backface strain technique in conjunction with video microscopy has been utilised to monitor the damage of the adhesive bondlines, the butts and the aluminium layers and successfully identified both the localised and the global damage in the MLD.Most of fatigue failures initiated at the stringer bondline edge and at the aluminium layers where the butt was located. A careful design should be made to reduce the stress concentration at the stringer edge and to avoid positioning the butts at the upper layer of aluminium close to the stringer edge.

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Review of surface pretreatments for aluminium alloys

Cited by 298 publications

References 50 publications

Novel methods, incorporating pre- and post-anodising steps, for the replacement of the Bengough–Stuart chromic acid anodising process in structural bonding applications

Novel methods, incorporating pre- and post-anodising steps, for the replacement of the Bengough–Stuart chromic acid anodising process in structural bonding applications

Fatigue and fracture assessment of toxic metal replacement coatings for aerospace applications

The static and fatigue responses of aged metal laminate doublers joints under tension loading

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