Problems with epoxy coating

Coatings such as modified epoxies, coal-tar epoxy, or solvent-borne epoxy have been used by many shipbuilders since 1998. The problem with these coatings is that the lifetime of these coatings is such that they can give protection for only 8-10 years, which is less than the design life of the vessels. These coatings are not resistant to the temperatures in double-hulled tankers and the bacteria that causes pitting corrosion on the bottom of tanks. The use of solvent-free epoxy on the top and bottom of a crude tanker should prevent corrosion of the tanker. 

Elevated temperatures are necessary for cure and the chemical resistance of the laminates is inferior to those from unmodified resins. Because of problems in handling, the polyamides have found only limited use with epoxy resins, mainly for coating and adhesive applications. 

Methanol tanks can be made from stainless steel, carbon steel, or fiberglass (using resins compatible with methanol). The steel tanks are welded together while the fiberglass tanks are molded around a form with the ends glued on. Some steel tanks are coated internally with an epoxy to prevent corrosion over time. The epoxies made for gasoline are not compatible with methanol and will come off the walls of the tank within a short time, causing major problems with... 

Other less sophisticated evaporation techniques are, for instance, the wrapping of W cods with Pt wire. Only small amounts of Pt can be vaporized, because alloying with the hot W occurs. The problem is also found with electrodeposited Rh on W coils. Other metal powders like Ru can be glued on W wires with epoxy cement. Slow annealing drives off the carbonaceous residue leaving Ru coated on W. The... 

Higher molecular weight epoxy resin hardeners such as fatty polyamides do not have the problems associated with amines and amine adducts. These reaction products of dimer and trlmer acids with polyfunctional amines provide films with fewer surface discontinuities. Polyamide cured epoxy coatings are more forgiving than amine cured epoxy coatings since they require less demanding surface preparation. Also, mix ratios are less critical for poly-amide/epoxy coatings (56). 

Epoxy coated rebars present particular problems to determining the corrosion condition of the Steel. In the first place the bars are electrically isolated from the concrete except at areas of damage. The size and locations of the areas of damage are obviously unknown. Attempts to carry out reference electrode potential surveys and linear polarization measurements have therefore been unable to come up with definitive criteria for corroding and non-corroding areas. The other problem is that the bars are isolated from each other, therefore a connection must be made to each bar measured to be sure that there is electrical contact. 

United States and Canada also apply them. Membranes come as two main types, a liquid that solidifies in place, and a sheet that is stuck to the concrete (see Section 5.3.3). The main problem with waterproof membranes is similar to that of epoxy coating rebars they must be applied without defects. Defects can occur as blow holes, penetrations or mechanical damage to the liquid applied types, or cuts, tears, bad joins or perforations in the sheets. Either type of membrane can be damaged by the overlay of asphalt, either by its heat or mechanical damage from the aggregate particles. 

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