Surface pretreatments etching treatments

While etch primers, also known as pretreatment primers and wash primers, can be regarded as priming paints which promote their own adhesion by etching the metal surface, they may also be regarded as phosphate/chromate etching treatments which leave an organic residue on the surface to form the basis of the subsequent paint scheme. A detailed account of the etch primers has been given by Coleman . 

Figure 12 represents a cross section of a plated sample of ULTEM 1000 having a peel strength of 118 g/mm. Little physical surface change of the plastic has occurred as a result of the pretreatment steps. Figure 13 is a cross section of copper plated ULTEM 2312. While a mechanical component to adhesion is present, it is much less than that found in traditional swell and etch treatment (Figure 2). Physical alteration of the plastic is confined to the outermost 25ii. The bulk properties of the plastic (flexural strength, electrical resistivity) are unaffected by this new process (Table I).

Pretreatment is necessary to achieve a clean surface on the piece to be coated. To remove fat, oxides, and other impurities from the surface, defatting, etching, and descaling operations are carried out, which are then generally followed by a precoating step. In the case of aluminum plating, a prelayer of nickel, cobalt or iron or alloys of these metals (0.5-2 pm) is applied. Each treatment step is followed by one or more rounds of washing and conducted in such a manner as to minimize loss and to recycle valuable material [28, 29, 33, 127]. 

Pretreated (enzymatic and enzymatic-I-hydrogen peroxide) knitted wool fabrics were treated with argon and atmospheric air plasma to improve adsorption capacity (Demir et al., 2010). After plasma treatment, a chitosan solution was appUed for antimicrobial effect. The treated fabrics were evaluated in terms of washing stabiUty as well as antimicrobial activity. The surface morphology was characterized by SEM images and Fourier transform infrared (FilR) analysis. The results indicate that the atmospheric plasma treatment had an etching effect and increased the fiinctionahty of wool surface. Atmospheric plasma treatment also enhanced the adhesion of chitosan to the surface and improved the antimicrobial activity. 

In the practice of adhesive bonding for applications in construction, surface pretreatment is likely to be the most difficult process to control. The choice of treatments must be tempered by the scale of operations, the nature of the adherends, the required durability, the adhesive to be used, and the cost. The performance of joints constructed with cold-cure epoxies is likely to be critically dependent upon surface preparation, as exemplified by the experience of the Scottish Irvine Development Corporation. In 1978 they elected to use vertical externally-bonded steel plate reinforcement to strengthen the abutment walls of three pedestrian underpasses. A year later, the plates were reported to be falling off, accompanied by extensive interfacial corrosion the steel surfaces had been abraded by hand, and the concrete surfaces chemically etched. 

Epoxy does not adhere well to untreated copper surfaces.This means that some type of treatment must be applied to the innerlayer before lamination. One option is to use double-treated copper, discussed earlier. Double-treated copper has a rough surface with a treatment supplied by the material vendor. Many ML-PWB fabricators report excellent results with double-treated copper. Others report problems with contamination and difficulty with rework. The alternative to using pretreated copper foil is to use a chemical treatment after etching. 

As discussed below, the classic example of the problem of oxide stability upon exposure of bonded joints is with aluminium and its alloys and this aspect has therefore been investigated in detail by the aerospace community. Particularly, the fundamental micro-mechanisms have been studied in order to explain observations such as those shown in Fig. 8.10, which reveals the effect of three common aerospace surface pretreatments upon the subsequent durability of the adhesive joints. The three treatments which have been studied in some detail are chromic acid etch (CAE), chromic acid anodize (CAA) and phosphoric acid anodize (PAA), and details of the processes were given in Section 4.3.4.5. 

The surface pretreatment for titanium is the well-known nitric hydrofluoric acid etching by a sodium bifluoric solution (see ASTM D2651 01). Some proprietary deviations from this basic treatment are taken by manufacturers. For example, hold release mechanism brackets in titanium alloy (Ti6Al4V) are used for mounting on antenna reflectors as parts of pyrotechnic mechanisms in order to deploy the reflectors in orbit before entering in operation (see Fig. 45.19). 

A low acid polyvinyl butyral-based pretreatment primer ( etch or wash primer are alternative names) is usually advantageous as the first treatment of a metal-sprayed surface before painting. Up to an equal volume of spirit soluble phenolic resin is used as a diluent to the polyvinyl butyral of conventional pretreatment primers. This has an incidental, but particularly valuable effect, in reducing the free acid available to penetrate into the pores of the coating. The modified pretreatment primer is highly water resistant and this helps to avoid damage due to condensation. 

The surface chemistry of Titanium alloys varies with each physical or chemical treatment. An example of ISS/SIMS results from a typical chemical pretreatment for T1-6A1-4V Is seen in Figure 1. Here the sample was degreased, etched in HN0-/HF and converted with a mixture of HF, NaF and Na PO In aqueous solution. Spectra from... 

Polyethylene terephthalate cannot be solvent-cemented or heat-welded. Adhesives are the prime way of joining PET to itself and to other substrates. Only solvent cleaning of PET surfaces is recommended as a surface treatment. The linear film of polyethylene terephthalate (Mylar) provides a surface that can be pretreated by alkaline etching or plasma for maximum adhesion, but often a special treatment such as this is not necessary. An adhesive for linear polyester has been developed from a partially amidized acid from a secondary amine, reacted at less than stoichiometric with a DGEB A epoxy resin, and cured with a dihydrazide.72... 

The etch resistance of poly (butene-1 sulfone) in fluorocarbon-based plasmas can be enhanced by prior treatment of the surface in an oxygen plasma. This pretreatment inhibits or retards the depolymerization reaction that characterizes normal etching in fluorocarbon plasmas, thereby permitting formation of a surface-modified layer which exhibits a substantially reduced etch rate. Pretreating PBS in an oxygen plasma enables it to be used subsequently in selective reactive-ion etch processes involving fluorocarbon plasmas to delineate submicron, anisotropically etched patterns. 

Pretreatment of PBS films in an oxygen plasma allows the creation of a chemically altered surface during subsequent fluorocarbon plasma treatment which provides enhanced etching resistance. 

In another set of experiments, PBTMSS samples were etched in the reactor which has been configured for sputtering, i.e., with a relatively high RF power (0.8 W/cm ) coupled to the upper target electrode. The wafer potential in this mode is low (80 to 130 V). The resist thickness was reduced by about 800 to 1000 A after 1 min. of such treatment (Figure 1, curve D). However, the surface of the polymer was smooth and defect-free. It was also found that a PBTMSS film pretreated by this method would withstand subsequent standard O2 RIE pattern transfer in a manner similar to the sample pretreated by the high-bias process, i.e., without the formation of surface defects. For convenience this pretreatment process will be referred to as "sputter-mode etching" (SME). 

The specifics of the degradation phenomena define the electrode pretreatment. In the case of mechanical treatment, the surface composition can vary due to heating [60], and this can be avoided by polishing in nonaqueous solutions [47] or by slowly cutting the surface layer while it is out of contact with air. Chemical treatment [60,61] will be discussed below in the context of the HTSC etching problem. 

Workers in Japan have shown that ultrasound can be used in electrochemical pickling and etching and smut removal in plating a beryllium-copper alloy [98]. The plating surface of Be-Cu alloys which are used commercially as electrical connectors, need to be pretreated by anodic treatment in an acid aqueous solution. These workers have shown that the smut may be effectively removed by application of ultrasound. This leads to a more resilient finish and a thickness of 0.2—3 p coating being achieved more rapidly. 

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