Compositions: coating or plastic – Coating or plastic compositions – Corrosion inhibiting coating composition
Patent
1999-06-03
2000-10-31
Green, Anthony
Compositions: coating or plastic
Coating or plastic compositions
Corrosion inhibiting coating composition
106 1405, 106 1441, 106 1442, 106 1443, 106419, 106431, 106436, 106442, 106445, 106447, 106448, 106450, 106456, 106457, 106459, 106460, 106461, 106466, 106471, 106499, 524175, 524176, C04B 1436, C04B 1600, C09C 104, C09D 508
Patent
active
061396109
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to chemical compositions and processes for inhibition of corrosion of metals. The preferred compositions are pigment grade products suitable for addition to primers, paints and other coating compositions.
BACKGROUND OF THE INVENTION
Organic protective coatings represent the most versatile and economical technology available for protection of metals against atmospheric corrosion. Corrosion inhibitive primer coatings are solid composites, comprising finely divided, usually multi-component, inorganic pigment phases dispersed in continuous organic polymer phases, which provide strong adherence to the protected metal substrates.
Although the physical characteristics of primers are reinforced by the dispersed inorganic pigment phases, they nevertheless remain permeable to O.sub.2, H.sub.2 O and air-borne pollutants. As a consequence, thin organic coatings do not prevent atmospheric corrosion of metals, unless they are specifically formulated with active corrosion inhibitor constituents, included in the pigment phase.
Contrary to appearances, a metal substrate protective primer, in equilibrium with its environment is a dynamic medium which accommodates several concurrently occurring physical and chemical processes, in which water, always present due to the resin phase's permeability, plays a critical role.
Water content affects the physical integrity of organic coatings in several ways. Most importantly, in this specific sense, it dissolves all soluble components (inclusive of pigments) to saturation concentrations and supports in situ diffusional transport processes of dissolved constituents. Water accumulates preferentially at metal-coating interfaces, causing loss of interfacial adhesion and more specifically supporting the electrochemical processes of metal corrosion. Paradoxically, in actively pigmented organic coatings water supports the inhibition of metal substrates' atmospheric corrosion, as well, by in situ solubilization of active pigments. Corrosion inhibitor pigment constituents of protective primers can be regarded as built in reservoirs of corrosion inhibitive species.
Commercially available chemically active corrosion inhibitor pigments used for Fe, Al, or Cu protection, belong exclusively to only a few classes of inorganic compounds, such as chromates, phosphates or polyphophates, molybdates, borates, silicates and phosphites of Zn, Ca, Sr, Ba, Al, Mg, Pb, Cr, Fe, or various combinations of these anionic and cationic species. Chromates and some of the latter cationic species, particularly Ba, Pb and Cr are known to be toxic. Transition metal derivatives of hydrogen cyanamide, particularly ZnNCN are also known for pigment grade application, limited, however, to special mirror backing coatings intended for Ag protection.
Generally, the active inhibitor species are the anionic constituents. Cations present, however, determine important physical properties of pigments such as solubility. Chromates, and specifically SrCrO.sub.4, are the standard of the industry, being the most versatile, applicable on all metal substrates such as Fe and specifically Al alloys and being highly effective, although toxic, pigment grade corrosion inhibitors. It is the redox activity of chromate species, accountable for their inhibitive efficiency which provides interference with corrosion processes in both, anodic and cathodic environments.
In contrast with chromates, all other active corrosion inhibitive pigments, more specifically, the anionic constituents of phosphates, molybdates, silicates, borates, phosphites and cyanamides are "redox inactive" under usual metal corrosion conditions. The consequences of "redox inactive" inhibitive mechanisms are significant. It can be generally stated that non-chromate based corrosion inhibitor pigments are less effective and qualitatively inferior, but non-toxic alternatives of chromates. As a consequence, for aircraft coatings used for aluminum protection and for coil coatings, where top corrosion inhibitive performances are req
REFERENCES:
patent: 4329381 (1982-05-01), Eschwey et al.
patent: 5176894 (1993-01-01), Sinko
patent: 5487779 (1996-01-01), Sinko
patent: 5558706 (1996-09-01), Sinko
Green Anthony
Wayne Pigment Corp.
LandOfFree
Hybrid pigment grade corrosion inhibitor compositions and proced does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hybrid pigment grade corrosion inhibitor compositions and proced, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hybrid pigment grade corrosion inhibitor compositions and proced will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2046413