Cleaning surface preparation sequence

The general sequence of surface preparation for ferrous surfaces such as iron, steel, and stainless steel consists of the following methods degreasing, acid etch or alkaline clean, rinse, dry, chemical surface treatment, and priming. The chemical surface treatment step is not considered a standard procedure, but it is sometimes used when optimum quality joints are required. It consists of the formation of a corrosion-preventing film of controlled chemical composition and thickness. These films are a complex mixture of phosphates, fluorides, chromates, sulfates, nitrates, etc. The composition of the film may be the important factor that controls the strength of the bonded joint. 

Titanium is widely used in aerospace applications that require high strength-to-weight ratios at elevated temperatures. As a result, a number of different prebonding surface preparation processes have been developed for titanium. These generally follow the same sequence as for steel and other major industrial metal substrates degrease, acid-etch or alkaline-clean, rinse and dry, chemical surface treatment, rinse and dry, and finally prime or bond. Mechanical abrasion is generally not recommended for titanium surfaces. 

Surface preparations must be carefully controlled for reliable production of adhesive-bonded parts. If a chemical surface treatment is required, the process must be monitored for proper sequence, bath temperature, solution concentration, and contaminants. If sand or grit blasting is employed, the abrasive must be changed regularly. An adequate supply of clean wiping cloths for solvent cleaning is also mandatory. Checks should be made to determine if cleaning cloths or solvent containers have become contaminated. 

In the case of concrete, the main reasons for preparing the surface before bonding are similar, namely (1) to produce a close fit between the adherends (2) to remove laitance and contaminants and to expose pieces of aggregate and (3) to produce a mechanically sound surface. Any typical sequence of steps in the process of concrete surface preparation should then include the removal of any damaged concrete and its replacement with new material, and the elimination of dust and other contaminants by brushing, air blast or vacuum. In some situations, additional steps like cleaning with a solvent to eradicate specific contaminants and application of a primer may be required. 

Surface Preparation - a sequence of treatments during which the surfaces of the adherends are made suitable for bonding. Depending on the adherends and adhesives, this may range from simple cleaning or degreasing to abrasion or complex chemical treatments. 

Fig. 7. Baseline-corrected ATR-FTIR spectra through the NHS activation sequence discussed in the text (a) freshly prepared H/Si(lll), (b) after functionalization with undecylenic acid, (c) surface (b) reacted with NHS/EDC for 1 hour at room temperature and (d) surface (c) after reaction with TEGamine. The background used is the spectrum of a clean oxidized ATR Si(lll) crystal for (a) and the spectrum of a Si(lll)-H surface for (b) and (c). Reprinted from [53].

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