Phosphoric acid cast iron

Exercise caution, and seek qualified assistance if in doubt. Iron objects are often covered with a layer of corrosion, which can vary from a light rust film to heavy, disfiguring scale.

Corrosion is undesirable when it detracts from an object's appearance and usefulness for display. Tannic acid is a complex organic acid found in plants. Different types of tannic acid are usually identified by the species of plant from which they come. When applied to iron, tannic acid reacts with the iron ions to form ferric tannate, a somewhat porous blue-black film whose degree of protection can be controlled to some extent by the method of application.

It produces a uniform finish that enhances the appearance of an object for more information on the effects of tannic treatment on iron, consult Selwyn Tannic acid should not be used on objects originally intended to be brightly finished or painted. As tannic acid produces a blue-black surface, it is suitable for wrought and cast iron, on which such a finish is appropriate. Composite objects, i. If this cannot be done, ensure that the tannic acid does not touch any material other than the iron.

Tannic acid can permanently stain materials such as wood, paper, wool, silk, leather, bone, horn and ivory. It is not necessary or desirable to remove light rust films or heavy corrosion before applying tannic acid. Tannic acid is a light, fluffy powder. Its colour varies from brown to golden brown, depending on the grade and the manufacturer. Like many natural plant products, tannic acid is a mixture of polymers, which means that a uniform formula for tannic acid does not exist and that the composition can vary among available brands.

As with any concentrated chemical, tannic acid poses a potential health hazard. Be careful not to inhale the powder or bring the acid in contact with skin. A dust mask should be worn when weighing and mixing the dry powder.

Tannic acid stains, so protective clothing gloves and a lab coat or full apron are advised. Safety glasses or goggles must be worn. If eyeglasses make it difficult or impossible to wear normal safety glasses, a full face shield should be used.

Tannic acid is a fine powder and, during preparation, a dust mask should be worn to avoid inhaling it. Measure and mix mL deionized or distilled water and 50 mL ethanol in a glass container. Plastic containers should not be used because they cannot be heated.

Weigh out the g of tannic acid. If you do not have a balance, you may be able to borrow one from a school science lab. To accelerate the process, gently heat the solution on the hot plate. When the tannic acid has dissolved, add enough deionized or distilled water approximately another mL to make a total volume of 1 L.

Test the pH of the solution using pH papers. If it is greater than 2. Always add acid to water, rather than vice versa, to avoid a violent reaction. With the aid of a dropper, add a few drops of the dilute phosphoric acid to the tannic acid solution, stirring continuously.

After adding about 10 drops, test the pH again. Continue the drop-wise addition of the acid until the pH decreases to between 2. This may require about 50 drops 2 mL of the dilute phosphoric acid, depending on the initial pH of the tannic acid solution consult Figure 1 for pH range. Unused dilute phosphoric acid can be washed down the drain with running water.

To achieve an even coating of ferric tannate, it is best to apply several coats of a dilute solution of tannic acid rather than one concentrated coat. Ten percent tannic acid, as prepared above, is too concentrated to produce a good result.Why don't fictional characters say "goodbye" when they hang up a phone?

If we can't tunnel through the Earth, how do we know what's at its center? All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. Hottest Questions. Previously Viewed. Unanswered Questions. Elements and Compounds. Wiki User Related Questions Asked in Chemistry What is the reaction between lead and phosphoric acid?

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Asked in Metal and Alloys What is a word equation for phosphoric acid and magnesium hydroxide? Phosphoric acid and magnesium hydroxide react to form magnesium phosphate and water.

Asked in Chemistry What do phosphoric acid and iron make? Asked in Elements and Compounds What is the Balanced equation for 2 iron hydroxide plus phosphoric acid? Asked in Elements and Compounds What is the product of phosphoric acid and hydrogen? Nothing, because they do not react with each other.

Asked in Acids and Bases How does phosphoric acid affect metal oxides?

Phosphoric acid

Phosphoric acid combines with iron oxide rust to form iron phosphide, which is inert - it doesn't corrode any further. The most common product made of phosphoric acid for this purpose is called Naval Jelly, available at any hardware store. Asked in Acids and Bases Why iron does not react with nitric acid? Nitric acid is oxidizing acid. When it reacts with iron it forms a protective layer of iron oxide over it. So it does not react further. Asked in Acids and Bases Will sulfuric acid react with calcium phosphate?

Calcium phosphate reacts with sulfuric acid to form calcium sulfate and phosphoric acid. Asked in Acids and Bases Phosphoric acid is a strong acid? No, phosphoric acid is a weak acid. Asked in Acids and Bases Does hydrochloric acid need air to react with iron? No, hydrochloric acid does not need air to react with iron.

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When hydrochloric acid reacts with iron, you will notice the reaction because of the bubbling. Asked in Acids and Bases What is the difference between orthophosphoric acid and phosphoric acid? Asked in Elements and Compounds What reacts with phosphate?

phosphoric acid cast iron

Asked in Elements and Compounds How do you mix zinc phosphate?We are working hard to ship as quickly as possible, while ensuring the safety of our associates. Send us your questions and our Total Support Team will respond by email or phone as soon as we can! Please note: Our Bristol retail store is closed until future notice. Rusted Metals: It's important to note that Ospho is a rust inhibitor coating and not paint.

Before applying, use a wire brush or wire wheel to remove loose paint, rust scales, dirt, oil, and anything else accumulated on the surface. After doing this, apply a coat of Ospho and let it dry overnight. Once the surface is dry, you can paint over it. How does it work? Ospho transforms rust to iron phosphate, an inert substance. You will know its doing its job when the metal turns black.

This means the chemical change has occurred. Very heavy rust can require two coats. Sometimes, a dry, grayish white powdery film develops. Simply brush off before painting. Bare or New Metal: Make sure new metal is clean and free of oils or grease before applying Ospho. After drying overnight, the surface is ready for paint. Galvanized Metal Treat galvanized metals differently, depending on how important appearance is.

If appearance is important, apply a singe coat of Ospho and let stand for 30 minutes or until metal is etched. Flush with water or wipe to a smooth finish. Once dry, the surface is ready for paint. If appearance doesn't matter, disregard the above. Simply apply a single coat, let dry overnight, brush off powdery residue, and paint. Painting Over Ospho Painting treated surfaces tends to yield more durable finishes, as moisture and oxygen are effectively sealed away from the metal.

Unlike thick paints, Ospho is as thin as water, going on easily and providing much more coverage about sq ft per gallon. This metal treatment works best with oil based paints and primers. Be sure to test before using with epoxy or latex paints. Suitable for use indoors or out. Also, excessive moisture or humidity may cause longer drying times and increase powdery residue buildup. Is it safe to use Ospho inside a metal bread box Can't throw out anything.

TB Rust primer is a primer that will turn the iron oxide rust! It is a primer and will need to be painted over so it will last. I am assuming the fence was galvanized when new. Galvanic coatings will become uneven over time depending on exposure to the elements.Dear sirs I would like to know more about the blacking process for steel and cast iron. I tried to find some specialized literature about this process in technical books, but unfortunately I didn't have success.

COM's colleague please if could some one help and indicate me, where I will be able to find details about this subject. Thanks in advance for the assistance, Best regards. Blackening on steel can be achieved by oxidation process using sodium hydroxide along with oxidising agents such as sodium nitrite and sodium nitrate. A typical formula for blackening on steel is given below. Any idea? Also dipping in blue colored oil seems to deepen the color If, any one has a basic idea about this?

Please give me an idea or let me know where it can be found in metal finishing.

phosphoric acid cast iron

My advance thanks to You. Hi, Janarthana.

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There are proprietary blackening solutions that operate at room temperature available from suppliers like EPI Electrochemical Products Inc. Some if not all are based on deposition of selenium compounds. We have an FAQ about black oxide and cold blackening. However, the best of the proprietaries, after decades of trial-and-error and gradual improvement, are still inferior to hot blackening in my personal opinion. So I would not propose a non-proprietary cold blackening process because the likely quality of the finish would likely be very low.

I'd say stick to hot blackening or purchase a proprietary room temperature bath. Good luck! There is really not much information about blacking of steels and cast iron available. All I can add is that it is simple and at everyone's site possible by means of a new blacking at room temperature.

You need no costly apparatus and have no harmful chemicals-no heating-up-no exhaust-no environmental problems.

phosphoric acid cast iron

It is as easy as dipping parts into paint. Digital version No longer published, but a copy is on Academia. Hi Klaus.


I claimed above as others have in letters here and in published articles that cold blackening is inferior to hot blackening.Login or Sign Up. Logging in Remember me. Log in. Forgot password or user name? Phosphoric Acid rust removal. Posts Latest Activity. Page of 1. Filtered by:. Previous template Next. Duct Taper. Phosphoric Acid rust removalAM. I want to use phosphoric acid to remove some rust on engine parts. Does anybody know if this will also affect aluminum, brass, insert bearings, etc.?

Tags: None. Phosphor will definitely eat brassmost likely other soft metals too JIM. Comment Post Cancel. SorryI may be wrong on the phosphor, it is sulphuric acid that definitly not good on brass. J Tiers. Whenever you get mixed metal parts, you will very likely get galvanic corrosion if you provide an electrolyte. Nearly any acid can provide that, as can bases like purple cleaner.

So even if the acid had no effect on some particular metals alone, it may well have an effect on a part that is assembled out of more than one of those metals.

That can be especially true if one of the metals is a very active metal like aluminum, etc. An example of a related issue with phosphoric: I got a large quantity of hole gages. There were a few extra sizes laying in the bottom of the drawer, and some had a little rust on them.

I did the phosphoric on the rusty ones, and had the first case of phosphoric eating the part that I had ever seen. The parts had some "martian canals" eaten into them.

All I can figure is that the parts were case hardened, and that they had some locked in stresses from hardening. The "martian canals" I figure were stress corrosion effects.

They looked much the same shape as the "mottling" on color hardened tools. I realized that I had left the parts in the phosphoric longer than I had intended. But it was not as long as I have in other cases where there was no problem. So, as safe as phosphoric generally is, it can still give a problem, and you should try a non-critical part if you have any doubt.Latest SubsTech articles Contact us Terms of use.

Dmitri Kopeliovich Phosphate coating phosphating is a conversion coating consisting of an insoluble crystalline metal-phosphate salt formed in a chemical reaction between the substrate metal and a phosphoric acid solution containing ions of metals zinc, iron or magnesium.

Conversion coating is a film of a chemical compound formed in the reaction of the substrate substance with another substance. This reaction distinguishes conversion coating from a conventional coating applied on the substrate surface without changing its chemical state. Examples of conversion coating are Anodizing electrochemical process of growing oxide film on the surface of anodically connected metal in an acidic electrolyte solution and Black oxide coating formed on the metal surface as a result of a chemical reaction of the metal atoms with an oxidizing agent.

Phosphating coatings are applied to steels, cast irons and aluminum alloys in order to increase their corrosion resistance, improve the anti-friction properties break-in, wear resistance, ant-galling, coefficient of friction and provide strong adhesion bonding for subsequent painting or other organic coating. Zinc phosphate coating is applied when increased corrosion resistance is required. Zinc phosphate withstands hours of neutral salt test. The coating color is gray of different tins: from light to dark.

Finer zinc phosphate crystals produce darker color. Dark gray color is also characteristic for the high carbon steel substrates.

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Zinc phosphate coatings may be applied by using immersion or spray technique. Light and medium weight zinc coatings do not require substrate surface activation. The substrate surface should be acid activated prior to heavy coating deposition. Zinc phosphate is used not only for non-coated Steels and cast irons but also for galvanized zinc plated steel parts.

Iron phosphate coating is applied when strong adhesion of a subsequent painting is required. In contrast to the solutions for Zinc phosphate and Manganese phosphate coatings, in which the metal ions are a constituent of the composition, to the iron phosphate solution iron ions are provided by the dissolving substrate.

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Iron phosphate coatings have very fine Grain structure. Iron phosphate is translucent therefore its color depends on the steel surface quality. The common color is blue or bluish-brown.Ospho is environmentally safe and non-flammable. OSPHO seals out moisture and prevents future rust from forming.

OSPHO is primarily used for bars-metal applications but can be used painted surfaces as long as the quality of the paint is not compromised. OSPHO isrecommended for use under oil based primares or paints. Test trial samples before using Epoxy or other paint systems.

A paint job will last much longer afetr an application of OSPHO because subsequent paint coatings attach themselves so tightly that moisture and oxygen cannot attack the metal. OSPHO is water thin and therefor covers a larger area ten painrt and goes on easily.

OSPHO is easily effective for exterior and interior work alike. OSPHO safely dissolves bleeding rust from many painted surfaces.

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Excess dew and humidity may prolong drying time, cause a reoccurrence of the drying process resulting in a powdery buildup. Spray equipment should be flushed out with water after using. Clean brushes with water. Merely remove loose paint and rust scale, dirt, oil, grease and other accumulations with a wire brush or pressure washer and let dry - apply a thin coat of OSPHO as it comes pre-diluted in the container.

Let dry overnight for a minimum of 24 hours, then apply whatever paint. Longer dry times may occur depending on temperature, humidity and over-application of product.

OSPHO has the consistency of water and treats up to square feet per gallon. When applied to rusted surfaces, OSPHO causes iron oxide rust to chemically change to iron phosphate - an inert, hard substance that turns the metal black.

Where rust is exceedingly heavy, two coats of OSPHO may be necessary to thoroughly penetrate and blacken the surface to be painted.


A dry, powdery, grayish-white surface usually develops when cured. Brush off any loose powder and wipe down with Mineral Spirits before painting. Let stand for approximately 30 minutes or until metal is etsched, then flush off with water, avoiding damage to adjacent areas. To avoid flash rusting on Ferrous metals, a top coat system may be required. Flush with water, avoiding damage to adjacent areas; or wipe to a smooth finish, let dry, then paint.

Where appearance is not important, one coat of OSPHO is recommended to thoroughly coat and etch the metal.

phosphoric acid cast iron

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