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The inhibition of marine corrosion of steel by 6‐amino‐2‐thiouracil (I) and its derivatives 6‐benzylideneamino‐2‐thiouracil (II) and 6‐p‐chlorobenzylideneamino‐2‐thiouracil (III) has been tested on laboratory scale using electrochemical technique which was performed on mild steel in sea water medium and on field scale through the incorporation of the compounds individually in marine paints compositions. The paints containing the compounds were applied on unprimed steel and the coated panels were tested in Alexandria Eastern Harbour water (Egypt). The electrochemical measurements indicated that both compounds (I) and (III) acted as cathodic‐type inhibitors, but the data of compound (II) showed neither cathodic nor anodic inhibition. Two marine paint compositions were prepared using different binder materials. The three compounds were added individually in both paint compositions. The paint composition based on the soluble resin material as a sole binder and containing compound (I) showed the best corrosion protection of its steel surface till more than two months followed by the paint composition containing compound (III). The same paint containing the compounds showed antifouling property for four months.

Four paint compositions were prepared, two of them based on vinyl copolymer as a binder and the other contain boiled oil in presence or absence of soluble resin material. Boiled oil based paints meet the most anticorrosion action and film property. Also, the anticorrosion potential of the paints depend on the type of ingredients and their ratio in the dry paint films.

4-Amino-3-thio-1,2,4-triazolidine (L,) and 4-amino-S-thi0-1,3,4-thiadiazole (L,,) as well as their metal complexes of the general formulae ML,.2Hz0 and ML,,CI (M; Pb(II), Cd(I1) and Zn(I1) were prepared. With Sn(II), we obtained Sn(L,), .2H,O and SnL,,Cl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 175% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6.7% by volume of tributyltin oxide to 15.8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae.