Anticorrosion paints

Zinc phosphate is now probably the most important pigment in anticorrosive paints. The selection of the correct binder for use with these pigments is very important and can dramatically affect their performance. Red lead is likely to accelerate the corrosion of non-ferrous metals, but calcium plumbate is unique in providing adhesion to newly galvanised surfaces in the absence of pretreatment, and is claimed to behave similarly on other metals in this group. 

Zinc chromate and zinc tetroxychromate have also been used successfully in anticorrosive paints. Both pigments function by releasing chromate ions which passivate the steel surface. In common with lead pigments, those... 

Alternating Current Impedance and Underfilm Darkening Studies on Acidic Water-Based Anticorrosive Paints... 

Anticorrosive paints containing pigments with either chemical or electrochemical action may induce formation of protective coatings at the metal-paint interlayer (Etz-rodt, 1993). These protective coating may be metal-substituted iron oxides iron phosphate precipitates or even a green rust - Fe Fe" 0HigC03 4H2O (Chemical Week, 1988). 

MIO is nontoxic, it is more environmentally acceptable than the lead and chromate based paints which are used to provide chemical protection in other anticorrosion paints and primers (Etzrodt, 1933). The highest quality (with respect to the flatness of the particles, aspect ratio, etc.) MIO comes from the mine at Waldenstein in Austria (Producer Karntner Montanindustrie), but there are also mines in Spain, South Africa and Western Australia. The supply of highest quality MIO, which used to be mined in Devon in England, was exhausted during the 1970s. This was one of the factors which prompted the U.K. workers to seek a method of making synthetic MIO (Carter, 1988 see Chapter 20). 

Another widespread application for flake zinc pigments is the coating of small articles with complex shapes (e.g., screws, steel springs, bolts, rivets) and for special anticorrosive paints (Section 5.2.11.1). 

Surface Preparation of the Substrate. This is extremely important for all methods of paint and coatings application. The failure of a paint system is often due not to the paint itself, but because of a failure in surface preparation. For example, an anticorrosive paint applied to a rusty surface will not be effective if the rust falls off taking the new paint with it. For wood and plastic surfaces, old paint or a weathered surface layer may have to be removed. For older metal objects, the removal of corrosion is often required. Sandblasting is one method to remove both the old paint and any corrosion. For new metal objects, a phosphate or chromate layer is often chemically bonded to the metal to provide a surface to which a coating can easily adhere. 

Before applying nonfouling paints, the cleaned surface of the hull is covered with an adhesive sublayer or a layer of adhesion promoter, and anticorrosion paint. In seawater tests panels covered with these paints do not foul even after 27 months of exposition panels covered with normal paints fouled by 100% already after 2 months. The serviceability of paints... 

Use Component of anticorrosive paints for use on iron, steel, and light metal alloys. 

Major polymer applications surface protective coatings (protective and decorative - automotive, metal cans, industrial flooring, anticorrosive paints), electrical/elec-tronics (printed circuit panels, conductive adhesives), composites (building/construction, marine, electrical/electronics, aircraft, communication satellites, automotive, pipes, consumer products), bonding and adhesives, flooring, tooling and casting, biosensors... 

Veleva, L., Chin, J., and del Amo, B., Corrosion electrochemical behavior of epoxy anticorrosive paints based on zinc molybdenum phosphate and zinc oxide, Progr. Org.Coat., 36, 211, 1999. 

Although it readily combines with oxygen, aluminium is resistant to atmospheric corrosion because a thin film of closely adherent oxide is formed which protects the underlying metal from attack. Aluminium powder is therefore used as a pigment in anticorrosive paints. 

Heavy-duty coating systems generally comprise two primer coats and two topcoats, modern system sometimes consist of one primer coat and two topcoats. The total dry film thickness (DFT) of such anticorrosive paint systems is 150 - 200 pm, each layer has a minimum DFT of 40-50 pm. Due to their excellent adhesion, the first and second primers prevent corrosion of the metal surface. The pigments and extenders allow the primers to react with ions (CD and SO4") that diffuse into the film from the atmosphere. The pigmented organic film also forms a barrier against humidity that may otherwise initiate a corrosive process. 

Fragata, F, Salai, RP, Amorin, C, Almeida, E. 2006. Compatibility and Incompatibility in Anticorrosive Painting—The Particular Case of Maintenance Painting. Prog. Org. Coat., 56, 257. 

Uses Thickener, flow modifier, leveling agent for air-diying aq. coatings, gloss paints, disp. paints, anticorrosive paints Features Improved film build and brushability Properties Whitish liq. dens. 0.99-1.10 g/cm (20 C) dynamic vise. 1000-15,000 mPa s flash pt. (PM) > 100 C = 30% act. 

Uses Thixotrope, antisagging agent, antisetfling agent for heavy duty primers and high build anticorrosive paints Features Particle swelling type Properties Powd. 100% solids UseLevei 0.5-2% (50-70 C)... 

Chem. Descrip. Solution of a polyurethane in water/diluent Uses Rheology control agent, associative thickener, flow aid, scrub resist. aid, film-former, pigment wetting agent for aq. polymer emulsions, coatings, syn. plasters, emulsion paints, adhesives, fillers, anticorrosive paints... 

Uses Hardener for epoxy resins in solv.-based paints (industrial and anticorrosion paints), solv.-free coatings, floor coatings, highly filled mortars for building trade, GRP, and encapsulating compds. for electronic components... 

Chem. Descrip. Coated calcium carbonate CAS 471-34-1 EINECS/ELINCS 207-439-9 Uses Filler in plastics (PVCplastisols, automotive underseals, polyolefin moldings and film), paints (matte paints, primers, anticorrosion paints) Features Very low absorp. inc. load ability in masterbatches Properties Wh. microctyst. rhombohedral powd. fineness 24% < 2 p dens. 2.7 g/cm bulk dens. 1.4 g/cm (packed) oil absorp. 13/100 g powd. brightness 96% ref. index 1.59 pH 9 hardness (Mohs) 3 Micro-Cel T-38 [Celite]... 

CAS 471-34-1 EINECS/ELINCS 207-439-9 Uses Additive in plasticized and rigid PVC, PVC coating, polyethylene, polyester, industrial and anticorrosive paints, putties, rubber Properties Powd. 0.5 mm mean diam. sp.gr. 2.7 apparent dens. 1.4 g/ cm (untamped) ref. index 1.59 pH 9 0.5 (aq. sol n.) hardness (Mohs) 3... 

---