What chemical will turn Rust into Metal the Best Many products on the market but which one will work?
RUST NEVER SLEEPS Corrosion is a complicated electrochemical process whereby a metal is converted to an oxide when exposed to a moist environment. Some metals, particularly bronze and brass, can form a stable protective corrosion layer, or patina, when they corrode. Iron, however, is highly susceptible to corrosion. Iron corrosion--that is, rust--is composed mostly of iron oxides. Unfortunately, iron oxides are unstable and provide no protection to the iron or steel below. Rusting iron will continue corroding if left unchecked. Rust converters are primers designed to be applied directly to a rusty surface. Unlike the standard scrape, prime, and paint regime, the user does not have to bring the surface down to bare metal. In fact, rust converters depend upon a layer of rust being present to be effective. First developed for specialty industries, these products are now seen regularly on the shelves of hardware stores and auto parts suppliers. There are two primary components in a rust converter: a tannin (usually in the form of tannic acid) and an organic polymer. The organic polymer provides a protective primer layer. Since the conversion reaction occurs faster in an acidic environment, some manufacturers will add oxalic or phosphoric acid to their rust converters to lower the pH and speed up the reaction. The tannin is the heart of a rust converter. It reacts with the iron oxide, converting it to iron tannate, a stable blue/black corrosion product. Tannins are a group of water- and alcohol-soluble natural products extracted from a variety of plants. Little is known about their true structure as they are complex and variable. Industrial research in the effectiveness of tannin solutions as rust primers began in the 1950s. Since then, tannic acid (a tannin) has become a standard conservation treatment for corroded iron artifacts found on archeological sites. In 1987, the Canadian Conservation Institute (CCI) in Ottawa, Canada undertook a long-term study of the effectiveness of nine commercial rust converters. Museum collections of large industrial objects, such as mining and agricultural machinery, are often stored unprotected outdoors. Devising a durable, effective, and easily applied rust inhibiting coating was necessary to preserve them. The results of their research have proved promising for collections, as well as for ironwork on all kinds of buildings PRIME DIRECTIVES Ideal as rust converters sound, they are only effective if used correctly. Though you don't need to scrape or chip down to bare metal, meticulous surface preparation is important. Rust converters will convert any rust they come in contact with, including fine particles. Follow the instructions and be sure to: * remove dust with a soft wire brush * thoroughly vacuum the surface * rinse away any soluble salts (from winter de-icing chemicals or marine environments) with water * degrease with mineral spiritsSimple to use, rust converters can be brushed or sprayed on the surface of the metal. Work neatly and consider masking off the area where you are applying the converter. The temperature of the metal should be between 50 and 90 degrees F, and there should be no risk of rain for 24 hours. Within 20 minutes after application the converter will turn any rust it touches coal-y black. The reaction is completely cured after 24 hours, longer if the ambient humidity exceeds 75% to 80%. Rust converters are formulated to be used as primers. Unlike traditional coatings, though, they must not be sanded. Nonetheless, a rust converter should always be followed with a compatible topcoat (check the manufacturer's recommendations). As you work, remember to never contaminate the stock solution by pouring used rust converter back into the bottle; only decant what is needed for the job. When it comes time to go shopping, bear it mind that not all rust converters are created equal. It's pretty safe to say that you get what you pay for. In order to be effective, a rust converter should have a pH of 2 to 2.5, the optimum range for forming a durable iron tannate film, and it should contain tannic acid. (In some converters the principal chemical is phosphoric acid, which reacts with iron and rust to form a phosphate coating--a corrosion retarder, but not on the level of a tannate coating.) The Material Data Safety Sheet available from the supplier or manufacturer should state the pH and main ingredients of any product you are considering. Like other paint products, rust converters have a shelf life that needs to be respected. Fresh rust converter should appear well-mixed and uniform. Reject any product that has settled--it will not be as potent. Later, store the rust converter where there is no danger of frost, and discard any quantities that have been allowed to freeze. Rust converters are versatile and ideal for both old-house exteriors and interiors. Though they won't render ironwork maintenance-free, they do make the task easier and more effective.