Epoxy primers

As discus.sed earlier, puny filling is generally not advisable unless the surface is poor, uneven or has pin holes. If is advisable to use primer surfacer, which provides a thicker coal and helps to fill such surfaces. The epoxy primer is thicker and may do this job in most cases. 

Suitable paints for use underwater include vinyl resin systems, coal tar paints over inorganic zinc-rich primers, and some coal-tar epoxy primers have also proved themselves Special paints are available for application under water, e.g. epoxy modifications with polyamides. 

Figure 19.60 illustrates a steel surface which should have been blast cleaned to a high standard before being coated at works with a zinc-rich epoxy primer and on site with two-pack intermediate and finishing coats. After exposure for 18 months in a marine environment, flaking millscale from beneath the paint was observed, and a survey showed that the paint... 

A484 Baseplate epoxy primer BSPL EPOXY c 20 ... 

Wedge Test. The adhesive bond durabilities of the Inhibitor-treated 7075-T6 surfaces were evaluated by wedge tests (ASTM D-3762) on bonded specimens using the FM 123-2 epoxy adhesive to simulate the epoxy primer. The specimens were placed In a humidity chamber at 65°C and 95% relative humidity and removed at specified time Intervals to record the crack tip locations after each examination, they were returned to the humidity chamber. 

In contrast, hydrolyzed silane compounds, presumably adsorbed as oligomeric films, confer corrosion resistance in both hydrating and Cl environments. These inhibitors can also couple with applied epoxy primer or adhesive formulations to further protect the metal against corrosion by strengthening the metal-epoxide bond. The organosilanes do not appear to affect the curing process, e.g., % crosslinking, of the polymeric epoxy systems. 

Anticorrosive pigment Air- drying alkyd primers Alkyd- melamine primers 2-Compo- nent epoxy primers 2-Compo-nent acrylic isocyanate primers Chlor- inated rubber primer Aqueous polymer dispersions Poly(vinyl- butyral) primers Electro- deposition coatings Mirror coatings References... 

The usual approach to good bonding practice is to prepare the aluminum surface as thoroughly as possible, then wet it with the adhesive as soon afterward as practical. In any event, aluminum parts should ordinarily be bonded within 48 h after surface preparation. However, in certain applications this may not be practical, and primers are used to protect the surface between the time of treatment and the time of bonding. Primers are also applied as a low-viscosity solution which wets a metal surface more effectively than more viscous, higher-solids-content adhesives. Corrosion-resistant epoxy primers are often used to protect the etched surface during assembly operations. Primers for epoxy adhesive systems are described in Chap. 10. 

Micaceous iron oxide epoxy primer High-build epoxy lining... 

Cohen, S.M. Electrochemical impedance spectroscopy evaluation of various aluminum pretreatments painted with epoxy primer. J. Coatings Techn. 1996, 68 (859), 73. 

The coating is two-component and needs mixing on-site prior to application. It can be applied either using conventional airless spray equipment or by brush or roller. A final thickness of 1 mm to 2 mm can be obtained with two coats. Pretreatment of the substrate with an epoxy primer ensures good adhesion. Defects in the concrete or brickwork are sealed with an elastomeric sealant which is resistant to the fluid being stored in the tank. 

Winterpoxy. [Potter Int L] Low tenq>. curing polyamide epoxy primer and topcoat... 

The corrosion protection of the HMMWV was to be provided by the military coating specification Mil-C-46164 and the CARC. The CARC paint system consists of a surface cleaning, epoxy primer, epoxy interior topcoat, and a polyurethane exterior topcoat. The purpose of this coating was to provide chemical resistance (penetration of the coating) and to aid in the decontamination of the vehicle in case of chemical attack. The coating was to provide corrosion protection as well as... 

High-build high solids, good-wetting epoxy primer with aliphatic polyurethane... 

Although two-pack epoxy primers and polyurethane intermediate coats have high solids contents, they still contain significant amounts (20-30 wt%) of organic solvents. In polyurethane topcoats, the VOC is even higher. Anticorrosive, waterborne primers based on aqueous dispersions of two-pack epoxy resins and one-pack acrylic resins have been developed to decrease solvent emission. Waterborne, one-pack acrylic topcoats are also used. All of these waterborne paints contain 2 - 5 % organic cosolvents that are required for film formation. 

Prime coating is either a two-pack, zinc-rich epoxy primer with a DFT of ca. 30-40 pm, or a chromate-free, two-pack epoxy primer. Topcoats based on PVC copolymerisates, chlorinated rubber, silicone-reinforced epoxy esters, or alkyds were used for many years. Now, the standard European topcoat is based on acrylic resins with terminal epoxy groups that are cross-linked with amine adducts or aminoamide resins. 

Two-pack epoxy primers with chromate-free pigments show the best performance. They are applied with a DFT of ca. 80 pm, and simultaneously form the anticorrosive primer and a sandable filler. They can protect the metal substrates against corrosion. 

The metals are joined by spot welds and rivets that may cause electric currents in the Joining areas. Specially designed epoxy primers prevent corrosion in these areas. At ambient temperature epoxy primer fillers dry thoroughly in about 16 h. Since this is too long for assembly lines, they are normally cured in ovens (80 metal temperature). 

Epoxy primers cured with amine adducts or polyamides, pigmented with zinc, zinc chromate and potassium chromate, strontium chromate, or, more recently zinc phosphate and calcium phosphate... 

Epoxy primers cured with amine adducts, containing inert pigments (usually iron oxide)... 

Epoxy primers, zinc-rich, cured with polyamines or polyamides... 

Epoxy primers are used as general-purpose primers on steel, galvanized steel, and aluminum, and under all types of finishes. These primers give excellent corrosion resistance on steel. Acrylic primers have a corrosion resistance similar to that of epoxy primers, and are used primarily under fluorocarbon finishes because of their superior intercoat adhesion. 

A one-pack primer based on chlorinated rubber or chlorosulfonated polyethylene (as is conventional with galvanized surfaces) or a two-pack epoxy primer is then applied. The primer can be coated with a topcoat system that is usually formulated with medium or long oil alkyd resins [11.39]. 

Water-based epoxy primers are ideal for damp porous substrates, as such primers will penetrate to an adequate depth to ensure good adhesion and produce a sound surface for bonding. Emulsifiable resins and hardeners are available, and the better systems deactivate the emulsifier system during cure to ensure that the cured system is not unduly water sensitive (Section VI.A). Solventless epoxy primers are used for bonding new concrete to existing concrete. Polyamide hardeners are preferred because of their ability to cure satisfactorily in the presence of water. Accelerators and diluents may be added, but fillers are generally omitted. The primer is applied to the existing concrete, and the fresh concrete cast before the resin has set (Section VI.B). 

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