CN1234079A

CN1234079A - Advanced galvanic corrosion protection

Info

Publication number: CN1234079A
Application number: CN97198948A
Authority: CN
Inventors: 托马斯J·加罗申
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 1996-10-21
Filing date: 1997-09-30
Publication date: 1999-11-03
Also published as: ID18594A; EP0950127A1; CN101063206A; DE69733317T2; ZA978931B; WO1998017841A1; KR20000052682A; BR9712540A; EG22317A; ES2238731T3; SA97180556B1; EP0950127B1; JP2001502757A; DE69733317D1; KR100334213B1

Abstract

A method for reducing the galvanic corrosion of dissimilar metals in contact with one another wherein the exposed surface of the more noble metal is coated with a metal more galvanically compatible with the less noble metal.

Description

Advanced galvanic corrosion protection

The protection of relate generally to metal of the present invention under corrosive environment is specifically related to be used for the protection of the copper-aluminum heat exchanger of conditioner.

Thereby, two kinds of dissimilar metals produce galvanic corrosion when forming pair of electrodes when existing to be in contact with one another under the electrolytical situation.The expensive metal that gets more (galvanic series is higher) is provided for the surface-area of reduction reaction, and the expensive metal that gets less (galvanic series is lower) then corrodes in an oxidising process.Take place at most in the oxidation of the interface place of two metals, but also can occur in from actual interface a distance.In the coastland, the most general ionogen is airborne salt solution.It is far away that tiny salt water smoke can be blown to 50 miles on bank off sea upcountry.The sulfurous gas that industrial pollution produces also forms an ionogen when it combines with airborne moisture.

The usual method that prevents galvanic corrosion is the metallic surface that exposes with various paint application.Owing to many reasons, the effect that these protectives apply is very limited.The subject matter that applies is that it prevents that corrosive validity is by being exposed to environment as reducing in ultraviolet ray and the acid rain.Another common issue with is that coating material often is not to stick in the substrate well, and in fact peels off or eat away and expose metal base.And this protective coating is porous and allows ionogen to pass substrate surface and connection electrode is right.In addition, the surface applications protective coating at some article can play opposite effect to its performance.

By aspect the trial in the work-ing life of extension fixture, having obtained success in various degree with the traditional copper-aluminum heat exchanger of various coated materials.These coated materials usually reduce the thermal heat transfer capability of device, and adhesion property is poor, can not penetrate might be exposed to zone in the corrosive atmosphere.

The present invention usually provides a kind of advanced person's galvanic corrosion protection.According to the present invention; one by two kinds of metals in; a kind of metal is morely more expensive than another kind of; this expensive outside surface of more metal that gets is with a kind of and expensive that less metal is handled at metal compatible aspect the galvanic corrosion; to form a protective layer between two kinds of dissimilar metals, this protective layer prevents that reduction reaction from appearring in electrode pair.The present invention has significantly reduced when two kinds of dissimilar metals and has the redox reaction process that occurs when being in contact with one another under the electrolytical situation.

Fig. 1 is the stereographic map of the heat exchanger that heat exchanger tube is housed handled according to the inventive method.

Below with reference to the galvanic corrosion protection that is used for copper-aluminum heat exchanger the present invention is specifically described.Yet apparent, those skilled in the art are not limited to this specific examples, and can be used to make dissimilar metal having the many configurations that are in contact with one another under the electrolytical situation.

Fig. 1 illustrates a finned-tubes exchanger 10 that typically is used for air-conditioning plant.This heat exchanger comprises one or more flow circuits that are used for putting by heat exchanger unit cooling agent.For ease of explanation, heat exchanger 10 comprises one by the single flow circuits pipe of forming at an incoming line 3 and an outlet line 4 of the connection of heat exchanger 10 1 end places by one 90 ° of bend pipes 52.Yet, obviously can in this device, increase more circuit according to the requirement of system.This device also comprises the radiator element 6 that a series of tabular elements of radial arrangement that separated by the length direction on longshore current moving-wire road are formed.This radiator element 6 is bearing in the assembly between a pair of end plate 7 and 8, with to the gas nationality to cross circuit pipe 2 and the gas flow channel between the radiator element 6 that separates limits.

As mentioned above, the heat exchanger of this form is exposed usually and is used in corrosive environment.In a typical configuration, the heat exchanger of this form is made the circuit flow duct and is adopted the copper pipe radiator element then to adopt aluminium.Fin arrangement become contact with the circuit pipe and by conduction heat transfer and then by to the circuit pipe on every side the convective heat transfer of mobile gas (being generally air) dispel the heat and heat discharged from the circuit pipe.In the circuit tubular construction, adopt copper to be and repair because it has good heat transfer characteristic, protection against corrosion and is easy to.Radiator element adopts aluminium to be because it has good heat transfer characteristic, is easy to make and low cost.Heat exchanger all adopts copper and all adopts aluminium avoiding the galvanic corrosion problem in some application scenario, but cost obviously improves.

Aluminium is very low on galvanic series, promptly compares lessly expensive with copper.Oxidation or corrosion when therefore, aluminium contacts with copper under having electrolytical situation.In structure shown in Figure 1, the interface of circuit pipe and radiator element is and produces electrode pair part and aluminium radiator fin generation corrosion part.In case radiator element corrodes in the intersection, this radiator element promptly no longer contacts with the circuit pipe, like this, because radiator element has lost its ability that heat is conducted from the circuit pipe, so heat exchanger effectiveness reduces greatly.

As below will specifying, according to the present invention, the exposed surface of circuit pipe 2 is with aluminium or one washing or denseization compatible with aluminium on galvanic series.Owing between aluminium coating and aluminium radiator fin 6, do not form electrode pair, so aluminium is best candidate metals.Yet, active metal such as zinc, tin, magnesium, gallium, cadmium and the plumbous degree that also will reduce electrode pair, thereby the oxidation rate of reduction fin material.

Is to carry out before the assembling of heat exchanger 10 with aluminium to the coating or surperficial denseization of copper wire pipe 12.The calorize of copper is well-known way and can be implemented into a levels of precision, in fact to eliminate the above-mentioned problem that is used to prevent the coating of corrosive tradition.Some courses of processing that are used for making the copper pipe calorize are that industry is existing and be used to the present invention.This coating procedure comprises hot dipping, electroplates, fills aluminium paint and coating and thermospray.The surface concentration process comprises ion vapor deposition, chemical vapour desposition and physical vapor deposition.

Main aspect of the present invention is to carry out the production of the even coating of aluminium on the whole surface of flow circuits pipe 2.Regardless of the process of being considered, variablees such as the preparation of circuit tube-surface, circuit pipe preheating temperature, coated component and coat-thickness all must carefully be controlled, to reach the distinctive result of the present invention.The preparation of circuit pipe exposed surface is preferably removed surface oxide layer from copper, adhere well on the circuit pipe to guarantee coating material.Many surperficial set-up procedures are existing in the industry, comprise adopting reducing gas, flux and sandblast.Circuit pipe preheating temperature should be controlled between 24 ℃ and 600 ℃, to prevent copper dissolution and limit the intermetallics growth in coating procedure.

The assembling of heat exchanger thereafter is preferably coating and has high ductility, so that can not damage coating.The ductility of coating partly depends on the composition of coating and the thickness of coating.As mentioned above, any oxidation rate that more can the metal ingredient compatible aspect electrochemistry will reduce radiator element 6 with fin material than circuit tube material, and the ideal coating material will mate with fin material fully.Consider to adopt some aluminium alloy among the present invention, comprising aluminium that is combined with silicon and the aluminium that is combined with zinc.Coating must be enough thick in to prevent that ionogen from penetrating.Yet, because any coating all has detrimental action for the heat passage of device, so should avoid blocked up protective layer.The optimum thickness range that the present invention considers is 0.1 mil to 2 mil.

Claims

1. one kind prevents that one is configured to first surface electrochemistry corroding method contacting with one second, described first by one than forming not as good as second expensive metal, described first has one and is suitable for the surface that contacts with described second surface, may further comprise the steps:

With certain expensive exposed surface that gets second of less metal treatment.

2. the method for claim 1 is characterized in that, the exposed surface that the treating step comprises with second of expensive less metal pair applies, to form expensive a less metal level at described second exposed surface.

3. method as claimed in claim 2 is characterized in that, and is described expensive that less metal layer thickness is between about 0.0001 to 0.002 inch.

4. method as claimed in claim 3 is characterized in that, described coating procedure is a hot dipping process, an electroplating process, a painting process or a diffusion coating procedure.

5. the method for claim 1 is characterized in that, described treatment step is a surperficial concentration process.

6. method as claimed in claim 5 is characterized in that, described treatment step is an ion vapor deposition process, a chemical vapour deposition process or a physical vapor deposition process.

7. the method for claim 1 is characterized in that, mainly is made up of copper for described second, mainly is made up of aluminium for described first, and described expensive less master metal will or comprise silicon or the aluminium alloy of zinc is formed by aluminium.

8. the method for claim 1, it is characterized in that, mainly form for described second, mainly form for described first by aluminium by copper, described so expensive that less metal comprises an expensive element of aluminium that select, too late from the group by zinc, tin, magnesium, gallium, cadmium, lead and combination thereof.

9. heat exchanger of making according to the method for claim 1.

10. heat exchanger as claimed in claim 9, it is characterized in that, described first is a radiator element made of aluminum, described second is a circuit pipe that is made of copper, described expensive that less metal is selected from the group by aluminium, silumin, aluminium zinc, zinc, tin, magnesium, gallium, cadmium, lead and combination thereof.