Corrosion-inhibiting poly(arylene sulfide) coating compositions

#This invention relates to corrosion-inhibiting poly(arylene sulfide) coating compositions and to processes which employ the corrosion-inhibiting poly(arylene sulfide) coating compositions in the formation of cured poly(arylene sulfide) resin coated iron or iron-containing laminates.

#In general, it is broadly known to coat iron and iron-containing alloys with poly(arylene sulfide) coating compositions to form cured poly(arylene sulfide) resin coated iron or iron-containing alloy laminates. Representative of some of the prior art coating and curing disclosures are set out in Tieszen et al. U.S. Pat. No. 3,622,376, Tieszen U.S. Pat. No. 3,634,125 and Grimes et al. U.S. Pat. No. 3,701,665. Although these and other prior art processes are useful in the preparation of cured poly(arylene sulfide) resin coated iron or iron-containing alloy laminates, it has now been found that corrosion and rust products can form on the surface of the material exposed to moisture and air during coating and/or curing of iron or iron-containing alloys which are deleterious to the recovery of a cured coating which is continuous, uniform, smooth and free of exposed iron or iron-containing alloy substrate. It has now been found that uniform, continuous, smooth, non-pitted cured poly(arylene sulfide) laminate can be prepared from poly(arylene sulfide) coating compositions which selectively employ only certain corrosion-inhibiting agents.

#It is an object of the present invention to provide corrosion-containing poly(arylene sulfide) coating compositions.

#The following examples are presented further to illustrate the practice of this invention.

#A series of coating compositions containing poly(phenylene sulfide) (abbreviated hereafter as PPS) was prepared in slurry form by ball milling 100 parts by weight of PPS, 33 parts by weight of titanium dioxide, and 266 parts by weight of a water glycol mixture (50--50 by volume) to provide a slurry containing 33 weight percent solids. The PPS employed was a V-1 type resin having an uncrosslinked virgin PPS melt flow of 2000 determined according to ASTM D 1238-70, Condition L. Various meterials were tested for corrosion-inhibiting activity at various concentrations by dissolving or slurrying the materials with a small amount of water and then thoroughly mixing the slurried or dissolved materials into the ball milled prepared PPS slurry to provide a resulting test slurry containing corrosion-inhibiting test material. Steel test coupons were cleaned with acetone to remove oils or grease and subsequently grit-blasted. The test coupons were then spray-coated with the test slurry. The uncured coated coupons were then allowed to stand in a closed container to retard evaporation (about 50 percent relative humidity) for a period of 2 hours. At the end of the first hour, the coupons were examined for rust spots and if rust was observed the test was discontinued. If no rust was observed after the second hour, the coated coupon was cured for 30 minutes at 700.degree. F and again examined for rust or imperfections in the cured PPS coating surface. In another series of tests the PPS slurries were prepared as described above, the coupons were cleaned, grit-blasted and spray-coated as described above, the coupons were cleaned, grit-blasted and spray-coated as described above, the coated coupons were allowed to stand in a closed container over water (about 95 percent relative humidity) for a period of 2 hours. At the end of the first hour of the test period the coupons were examined for rust and if rust was observed the test was discontinued. If no rust was observed at the end of the second hour, the coated coupon was cured for 30 minutes at 700.degree. F.

#The inspection at the end of the first and second hours of the uncured coated coupons was done without magnification of rust spots which were visible to the naked eye. The cured coat was inspected under 20.times. magnification to detect small imperfections caused by poor adhesion to rust spots on the substrate and other surface irregularities.