Pretreatment degreasing

Degreasing - Mechanical Pretreatment - Degreasing according to Sections 7.1.1 and 7.1.2 suffices for most applications. 

With few exceptions it is more efficient and economical to use at least two different pretreatments, i.e. degreasing processes which deal with a) and b), and pickling processes which remove oxide and corrosion films. Degreasing comes first, as pickling processes fail on hydrophobic surfaces. 

First comes the pretreatment stage. After rust removal and alkaline degreasing, a zinc phosphate formulated pretreatment (see Section 15.2) is applied by dip or spray-dip. Crystalline iron-rich zinc phosphate forms on the metal surface at a coating weight of 0.5-4.5 g/m. ... 

There are numerous metal pretreatment techniques that can be used in addition to solvent degreasing. To obtain metal/polymer systems which exhibit strong initial adhesion it is usually sufficient to wash the metal with a solvent followed by an acid etch or sandblasting technique to remove any weak oxide layers and roughen the surface simultaneously. 

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... 

A variety of pathological changes of the liver occur with repeated exposures of rats, rabbits,guinea pigs and dogs to PCE. Hepatotoxicity is increased in rats pretreated with aroclor or phenobarbital. This observation as well as the urinary excretion of chlorinated metabolites points to the liver as a probable oxidation site (ref. 67). In man, acute intoxication has generally resulted from industrial degreasing operations. 

Mechanical removal of adhesive layers (sanding, rotating steel brushes, etc.) with ensuing degreasing has to be carried out as surface pretreatment. 

Mechanical surface pretreatment, followed by very careful degreasing. Carry out bonding immediately, since especially silver surfaces can change due to silver sulfide formation (dark staining). 

In most cases, adhesion fractures are a sign of insufficient surface pretreatment. In the case of mixed fractures, the reason is to be seen, with high probability, in an incomplete or uneven degreasing. The neglected degreasing after blasting can also be seen as a cause, if the compressed air has not been absolutely fat-free. A cohesion fracture may be the consequence of an adhesive layer not completely cured or of the application of an inadequate adhesive mix. 

The last chemical pretreatment step is the electrolytic or fine degreasing, in which the chemical cleaning power of an alkaline cleaner is enhanced by an electric current. The underlying mechanisms have not been fully clarified. Saponification of the esters of fatty acids may play a role. Furthermore, the evolving gas bubbles will tear off the last traces of contaminants from the surface. 

As the paint dries on the substrate, a firmly bonded film is formed. The properties of this film are determined both by the substrate and its pretreatment (cleaning, degreasing) and by the composition of the coating and the application method used. Drying of the paint on the substrate takes place physically (1-3) or chemically (4) ... 

Figure 3. Scanning electron micrographs of unfilled polyetherimide as received (upper left), pretreated according to the Standard 2312 process (upper right), or employing nitric acid (lower left) or hydrochloric acid (lower right) as the impregnator. The impregnator was inserted between the degrease and surface removal steps.

Reference (No) Discipline/ application Epoxide Adher. cold hot mat(s) Pretreatments (followed by degreasing) Adhesion promoters... 

The bonding of aluminium alloy components for structural engineering applications has been the subject of extensive research by the Dutch TNO Institute for Building Materials and Structures(19, 20). Apart from the evaluation and testing of a number of adhesive systems, experimental research was carried out on several structural details. Aluminium alloy surface pretreatment was by degreasing only, to represent a practical procedure. 

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