CN1004212B - Acid washing-passivating paste for stainless steel - Google Patents

Abstract

The present invention relates to a novel stainless steel pickling-passivating paste which can be extensively suitable for the cleanness of oxide at or near stainless steel welding seams and is particularly suitable for the removal of oxide skin which is kept on the components, for example, the sealing heads of stainless steel containers, etc. after the high-temperature processing of baking furnaces, etc., wherein the thickness of the oxide skin is from 2 to 3mm. The novel stainless steel pickling-passivating paste has the double functions for pickling and passivation, and stainless steel treated by the novel stainless steel pickling-passivating paste can recover the silvery original appearance of the stainless steel. The novel stainless steel pickling-passivating paste contains nitric acid and hydrofluoric acid and uses the thickening agent of magnesium stearate, the inorganic filler of magnesium nitrate and the corrosion inhibitor of sodium polyphosphate as carriers. The novel stainless steel pickling-passivating paste also has the advantages of low cost, convenient preparation, easy operation, simple post treatment, long storage time, little pollution to environment, etc.

Description

Acid washing-passivating paste for stainless steel

The present invention is pickling-passivation cream that a kind of stainless steel surface of novelty is handled usefulness.Be not only applicable to clean stainless steel weld joint and near oxide compound, be applicable to that more removing is through staying the heavy scale on the parts such as stainless steel vessel end socket after the processing of high temperature such as red stove.

Stainless-steel sheet is after welding or being processed into parts such as vessel head with high temperature such as red stoves, weld seam and near surface and that process can produce one deck oxide compound, and particularly the latter's thickness can reach 2～3mm.In the past, adopt mechanical grinding usually or remove these oxide compounds with the way that solution such as nitric acid carry out pickling.The resistance to corrosion of the big and infringement stainless steel of mechanical grinding effort itself.

And the way of employing pickling often must place parts of stainless steel and carry out pickling in the pickling tank of being furnished with solution such as nitric acid, and then carry out Passivation Treatment.This method not only floor space is big, complicated operation and dangerous, and the cost height, and also environmental pollution is serious.Meet large-scale stainless steel equipment and carry out conjuncted equipment of on-the-spot manufacturing and installation and many stainless steels and carbon steel etc., aforesaid method is just powerless.

In recent years, gradually in the Corrosion of Stainless Steel cream that adopts a kind of pasty state, it is sticked on pending in the world, remove oxide compound.This method is not owing to limited by steric requirements, simplified control, and cost reduces, and effective and environmental pollution such as alleviates at tangible advantage, and has progressively replaced above-mentioned traditional treatment process.

Known Corrosion of Stainless Steel cream all contains a certain amount of nitric acid and hydrofluoric acid, and different is the various carriers of preparation.Because the latter's difference can make the effect of corrod(o)kote paste that very big difference is arranged.People once adopted barium persulfate, calcium sulfate, kaolin, bentonite, silicic acid or diatomite, also adopted peroxidation aluminium, magnesium oxide or pure aluminium silicate as carrier.Yet mentioned reagent is owing to following many disadvantages is updated: or because it and hydrofluoric acid can react the corrosive nature of corrod(o)kote paste of having neutralized; Or because the density variation of its density and other component makes corrod(o)kote paste produce sedimentation too greatly; Or because it produces excessive erosion and damages stainless metalline with processed stainless steel surface; Or owing to viscosity makes corrod(o)kote paste take place to glide when the inclined-plane of handling stainless steel equipment or the vertical surface to clean inhomogeneous inadequately; Perhaps because of the dry and cracked crackle that occurs on treated side takes place easily.After this, people adopted the form of thermoplastics or duroplasts ball again, as polyolefine as carrier.With the corrod(o)kote paste that this class carrier is prepared, advantage is to have avoided sedimentation phenomenon, but still has following shortcoming to overcome: the chlorion in the chloride plastics can produce the excessive erosion effect to stainless steel; Often need the special wetting agent of use and make the cost costliness; Still can produce ununiformity during brushing, worse is that environmental pollution increases the weight of.Also the someone adopted organic thickening agent such as carboxymethyl cellulose and Walocel MT 20.000PV as carrier, but also was abandoned because of it can make corrod(o)kote paste lack to be difficult to after standing storage ability or the drying safety of handling and jeopardizing the operator.

Domestic also once had a lot of units that Corrosion of Stainless Steel cream was carried out exploration.Reported a kind of homemade pickling paste in " process water water quality and weldprocedure are to the Test Summary of Corrosion of Stainless Steel influence " as the publication of " field engineering communication " first phase in 1978, it is to be formed with a certain amount of acidic white earth modulation by 3 parts of hydrochloric acid, 1 part of nitric acid and 0.5 portion of vitriolic mixed solution.Owing to contain a large amount of muriates and sulfide in this pickling paste, understand serious environment pollution during use and stainless steel is produced local corrosion.

The DE3006007A1 German patent application of announcing in August, 1981 has proposed to prepare as carrier with basic metal hexafluoro aluminate the scheme of the corrod(o)kote paste that contains nitric acid and hydrogen fluoride solution.It is said that this invention has solved all deficiencies of all known corrod(o)kote pastes in the past with " alert people's simple and economical method ".But, this only is contriver's a hope, this prescription is not best far, corrod(o)kote paste with this formulated has following defective at least: the first, because basic metal hexafluoro aluminate has the moisture absorption and easy exsiccant performance, so it can be used as the thickening material use in corrod(o)kote paste, but simultaneously because its this performance can be brought two adverse consequencess again, the one, easily dry with the corrod(o)kote paste of its preparation, even caking, must constantly add water even strike and add water after splitting and could use; Two are to use time brushing back on the stainless steel treated side easily dry, even caking, and aftertreatment bothers very much, must just can remove residue by spatula.If water dashes, then must when luming as yet, not carry out, water also will apply certain pressure, causes around residue is splashed to.The second, basic metal potassium hexafluoroaluminate or sodium are the higher reagent of a kind of price, and its consumption will account for 35～65% of corrod(o)kote paste, thereby make this corrod(o)kote paste cost higher, be difficult to, particularly in the industry of the such developing country of China, use in a large number industrial.The 3rd, also be most important, this corrod(o)kote paste only can be handled near the oxide compound as weld seam reaches, and for the removing that reaches the oxide skin of 2～3mm, one class with thickness on the parts such as stainless steel vessel end socket of high temperature such as red stove processing, just powerless.This also be up to now all known corrod(o)kote pastes cause weakness.

Purpose of the present invention is to propose the acid-washing stainless steel-passivation cream of a kind of effect height, practical novelty, to overcome the deficiency of existing corrod(o)kote paste.So-called effect height will make this pickling paste can not only clean the black of stainless steel equipment welding back generation or the oxide compound of brownish black exactly, and can thoroughly remove the heavy scale on the parts such as staying the stainless steel vessel end socket after high temperature such as red stove are processed.Can also give full play to the special efficacy of pickling-passivation " step is clear ", promptly after pickling, can also carry out effective Passivation Treatment, reply argenteous looks of stainless steel stainless steel surface.So-called practical, it is with low cost that this pickling-passivation cream is had, and modulation is convenient, processing ease, and aftertreatment is simple, and the storage time is long, the little inaccessible various advantages of these existing corrod(o)kote pastes that waits of environmental pollution.

To achieve the above object of the invention, the acid-washing stainless steel that contains nitric acid and hydrofluoric acid-passivation cream with the present invention's preparation, adopted stearic magnesium acid, magnesium nitrate and sodium polyphosphate as carrier, its concrete composition scope is as follows: 2.2～2.7% or 1.4% Magnesium Stearate, 60～70% magnesium nitrates, 2.3～2.8% or 0.9% sodium polyphosphate, 8～14% nitric acid, 10～15% hydrofluoric acid, remainder are water.The main effect of above-mentioned each reagent is as follows: Magnesium Stearate adds as a kind of thickening material; Magnesium nitrate adds as mineral filler, is in order to increase adherence and perviousness; Sodium polyphosphate is a kind of inhibiter, can relax corrosive speed, makes corrosion equably to distributing all around; Nitric acid and hydrofluoric acid exist as etching reagent; Certain content of water is that the suitable viscosity of adjusting is necessary.Said components is modulated at together, and the comprehensive action that it mutually combines makes acid-washing stainless steel-passivation obtain various excellent characteristics as described below.

With the acid-washing stainless steel-passivation cream of the present invention's preparation, its principal feature is: one, effect height.This cream can not only be widely used in the cleaning of stainless steel equipment weld seam and nearly seam district oxide compound, and to through staying the removing of the thick oxide skin of 2～3mm on the parts such as stainless steel vessel end socket after the processing of high temperature such as red stove, has original effect.Because the present invention does not contain sulfide and muriate; show through series of physicochemical check and test evaluation; use this cream can not produce corrosive nature or damage its intensity and resistance to corrosion to stainless steel; on the contrary; after cleaning; can generate the oxide film protection layer stainless steel is played effective passivation, thereby strengthen its resistance to corrosion.The stainless steel surface of handling through the present invention can recover its argenteous looks.Two, cost is low.The reagent that the present invention adopts, its cost is lower than existing corrod(o)kote paste, than the prescription of DE3006007A1 cheap 2/3rds.This has just created effective condition for this cream in industrial a large amount of uses.Three, easy to use.The present invention's pasty state that is creamy white, its viscosity is suitable, does not need redistribution during use, also without any need for special utensil, only is applied to 1～2mm thickness with general hairbrush gently on stainless steel equipment or parts pending and gets final product.Neither can feel effort during brushing because of viscosity is too high, be unlikely to again on inclined-plane and vertical surface, to glide, more can not take place dry and cracked.Four, aftertreatment is simple.After coating this cream and surpassing 50 minutes, the residue that promptly available hard waste or useless cloth will rest on the cleaning face is wiped, and cleans with wet cloth again, and is promptly sparkling clean, need not carry out spatula; It is better to utilize the tap water flushing to clean, and uses normal pressure to get final product during flushing, and need not feed water applies certain pressure.Five, environmental pollution is slight.The residue that cleans can neutralize with Wingdale, and at most user's theres, also available ready-made calcium carbide is stuck with paste and neutralized, and can not produce reluctant environmentally harmful material.Six, the storage time is long.Acid-washing stainless steel-passivation cream with the present invention's preparation has stored more than 1 year, and not seeing has disassociation and deposited phenomenon, does not have any quality and changes.

In order to obtain best effect, provide following two embodiment.

Embodiment one: have the acid-washing stainless steel-passivation cream that cleans oxide compound and remove the heavy scale purposes concurrently.Its concrete composition is:

Magnesium Stearate 2.4%

Magnesium nitrate 62%

Sodium polyphosphate 2.4%

Nitric acid 14%

Hydrofluoric acid 14%

Remainder is a water.

Embodiment two: can be widely used in the acid-washing stainless steel-passivation cream that cleans oxide compound.

Magnesium Stearate 1.4%

Magnesium nitrate 62%

Sodium polyphosphate 0.9%

Nitric acid 8%

Hydrofluoric acid 10%

Remainder is a water.

Above-listed component is all calculated with weight percent concentration, and reagent can be used chemical analysis level reagent, also available technical grade chemical reagent during preparation.

Claims (22)

1, a kind of acid-washing stainless steel-passivation cream that contains nitric acid and hydrofluoric acid solution is characterized in that, it with thickening material Magnesium Stearate, mineral filler magnesium nitrate, inhibiter sodium polyphosphate as carrier.

Concrete composition scope is as follows:

(1) Magnesium Stearate 2.2～2.7% or 1.4%;

(2) magnesium nitrate 60～70%;

(3) sodium polyphosphate 2.3～2.8% or 0.9%;

(4) nitric acid 8～14%;

(5) hydrofluoric acid 10～15%;

(6) remainder is a water.

2, acid-washing stainless steel as claimed in claim 1-passivation cream, it is characterized in that, when its have concurrently clean stainless steel weld joint and near oxide compound and when after the processing of high temperature such as red stove, staying heavy scale effectiveness on the parts such as stainless steel vessel end socket, its concrete composition is preferably:

(1) Magnesium Stearate 2.4%;

(2) magnesium nitrate 62%;

(3) sodium polyphosphate 2.4%;

(4) nitric acid 14%;

(5) hydrofluoric acid 14%;

(6) remainder is a water.

3, acid-washing stainless steel as claimed in claim 1-passivation cream is characterized in that, near the oxide compound time spent it only reaches as the cleaning stainless steel weld joint, its concrete composition is preferably:

(1) Magnesium Stearate 1.4%;

(2) magnesium nitrate 62%;

(3) sodium polyphosphate 0.9%;

(4) nitric acid 8%;

(5) hydrofluoric acid 10%;

(6) remainder fire water.