Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2000-03-24
2001-10-30
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S218000, C510S234000, C510S245000, C510S253000, C510S255000, C510S261000, C510S363000, C510S398000, C510S401000, C510S405000, C510S421000, C510S434000, C510S477000, C510S480000
Reexamination Certificate
active
06310024
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition and method of using a composition in rust and/or scale removal.
The present invention more particularly relates to a composition that can be used for the removal of rust and/or scale from metal surfaces under safe conditions. Further, the present invention relates to a method of treating an aqueous system with a combination of components to remove rust and/or scale deposits from iron/iron alloy metal surfaces of the aqueous a system. More particularly the present invention relates to a simple, safe process with one treatment step to remove rust and/or scale deposits from metal surfaces without the use of strong acids while leaving a stable passivated magnetite coating.
BACKGROUND OF THE PRESENT INVENTION
It is known that aqueous systems, particularly industrial aqueous systems such as boiler systems, cooling tower systems, heat exchanger systems, desalination systems, paper mills, heating/cooling systems, fire service water, reactors, and the like are subject to the formation of deposits on the internal surfaces which are in contact with the circulating water. The removal of scale and iron oxide deposits, which arise either from the chemical reaction of the water with the metal surfaces of the system's piping and other parts, as well as from being present in certain water supplies, is necessary to prevent “under deposit corrosion” of metallic surfaces and for the maintenance of clean heat transfer surfaces to assure good thermal efficiency. A buildup of metal oxide will affect the rate of heat transfer, will cause the pipes to become clogged (limiting flow) and, in general, add to the corrosive aspect of the water. A metal surface which is exposed to a corrosive environment, such as water which contains dissolved oxygen and dissolved ionic inorganic solids will be subject to corrosion under the deposits of solids that form on the metal. If the deposits are not removed, under deposit corrosion can penetrate through the metal, breaching the containment. Once this occurs, fluid starts leaking from the system and the system must be taken off line and this portion of the system must be repaired or replaced.
A number of approaches have been attempted to create an effective rust and/or scale cleaner. The use of chelating agents or chelants are known for their ability to remove particular cations such as iron. Also, chelants tend to be somewhat specific with respect to which cations they will complex with and under what conditions. As disclosed in U.S. Pat. No. 5,183,573, the disclosure of which is incorporated herein in its entirety by reference, chelants function by essentially “locking” the metal into a soluble organic ring structure. The use of chelants, such as ethylene diamine tetraacetic acid (EDTA), along with dispersants is well known for removing iron, because iron has six coordination sites as does EDTA and iron is removed by EDTA since it forms a stable metal chelant with iron. This approach often results in clean waterside surfaces. However, the greatest drawback to this approach is that the reaction that removes oxidized metal is not self-terminating. The chelant will continue to dissolve the surface metal even after the corroded oxide coating is removed. This can lead to a very serious problem, the problem the cleaner was to prevent, i.e. perforation of the metal leading to tube failure or joint leaks. An attempt to solve this problem is disclosed in U.S. Pat. No. 5,171,477, the disclosure of which is incorporated herein in its entirety by reference.
Another approach is using high concentrations of aminoalkylphos-phonates, but these cleaners are expensive and leave a fresh metal surface which “flash rusts” leaving a thin film of the very oxide which was just removed. Disposal also becomes a problem with these cleaners in areas where phosphate discharge limits are legislated. The use of a carboxyalkyl, aminoalkyl hydroxyaryl sulfonic acid is also available, but this cleaner requires long time periods, i.e. weeks, to be effective. Organic compounds, such as hydroquinone and quinone have been used as iron oxide dispersants at high doses, but their cost is prohibitive and their use is restricted to alkaline pH ranges. Acid cleaners, such as, muriatic acid, sulfamic acid, etc. have been used, but the low pH's at which these agents work is hazardous and also presents disposal problems.
Methods of treating or removing iron contaminants, such as iron oxide, from aqueous systems are also disclosed in the following U.S. Pat. Nos. 3,806,459; 4,190,463; 5,022,926; and 5,223,146.
It would be very desirable to be able to quickly remove scale and/or rust deposits from metal surfaces under safe conditions without the use of strong acids. It would also be desirable to be able to remove scale and/or rust deposits from metal surfaces without the risk of perforating the metal wall of the system. Further, it would be desirable to be able to remove scale and/or rust deposits from metal surfaces while leaving a stable protective coating.
SUMMARY OF THE INVENTION
The present invention relates to a composition that is useful in rust, corrosion and/or scale removal that comprises: a) an inorganic reducing agent; b) a chelating agent; c) a low foam penetrating surfactant; d) a water soluble polymeric dispersant selected from anionic and nonionic polymers; and e) water.
The present invention also relates to a process of treating aqueous systems that contain metal surfaces by introducing the above composition into said systems.
The present invention further relates to a method of treating metal surfaces in preparation for coatings that comprises applying the composition above in an aqueous form to a metal surface.
DETAILED DESCRIPTION OF THE INVENTION
The composition of the present invention is a novel unexpected composition. Prior to the present invention reducing agents were heretofore unknown for use in rust, corrosion and/or scale removal in water systems, particularly in combination with the other components of the present composition. Prior to the present invention it was not known that a composition containing an inorganic reducing agent; a chelating agent; a low foam penetrating surfactant; and a water soluble polymeric dispersant would be an improvement in rust, corrosion and/or scale removal in water systems.
The composition and process according to the present invention takes advantage of the right combination of factors to provide improvement in rust, corrosion and/or scale removal in water systems. Since deposition is a process involving any or all of the following: formation of corrosion products, scale or the water born silts and biofilms formation, the cleaning of the deposit according to the present invention takes into account all of the contributing factors.
The present invention is a dramatic improvement over the art and the inventors have unexpectedly discovered that the reducing agent serves to convert the iron oxide to a more soluble form and to transform the pipe metal surface to a less reactive state by forming a magnetite coating on the surface. The penetrant serves to remove the biofilm residues which act as a glue entrapping metal oxide, silt, scale, and/or biological particles on the metal surface. The dispersant also helps to suspend iron oxide and silt particles in the bulk water. preventing re-deposition onto the metal surfaces, while the chelant helps hold some of the soluble metal in solution preventing re-oxidation and re-deposition onto the metal surface.
The composition of the present invention is able to quickly and inexpensively remove scale and/or rust deposits from metal surfaces under safe conditions without the use of strong acids and is thus a more environmentally friendly process. The cleaning time with the composition of the present invention can be in hours rather than the days it takes with some conventional products (non-acid products). The aqueous system is emptied of its contents for cleaning and the composition of the present invention is introduced in a one step appl
Gill Jasbir S.
Yorke Monica A.
Boyer Charles
Breininge Thomas M.
Brumm Margaret M.
Calgon Corporation
Gupta Yogendra N.
LandOfFree
Rust and scale removal composition and process does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rust and scale removal composition and process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rust and scale removal composition and process will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2577965