There are three general types of rust preventative products most commonly used in the marketplace today. Each have their advantages and disadvantages for use. This rundown of rust preventative basics provides some descriptions of each products and why one may be better for you to use than another. When choosing a rust preventative, keep in mind the corrosion protection required, equipment available for applying the product, drying capabilities, long term use of product, post processes, and the R.P. film characteristics.
Traditional Petroleum-Based Rust Preventative
These types contain a non-synthetic, oil-based material to provide corrosion protection. For years these have been used for long term, robust corrosion protection. There are two general types: those that are used as an emulsion in water and those that displace water. The emulsion type is more prevalent, but the water displacing types, although a little less common, work just as effective if maintained properly. They can be more expensive than other R.P. methods, since their primary ingredients are typically petroleum derivatives and products. However, they are very durable and robust when it comes to protection and bath life. They are also a bit messier than other applications, leaving a slightly oily film on the parts and surrounding floor areas. However, the emulsion types, when dried properly, leave a film which is not very noticeable on the finished goods. The emulsion types typically run at a concentration of ~10% v/v, while the water displacing oil R.P. products are typically used neat (100% v/v). An alkaline cleaner or solvent degreaser is required to remove these R.P. coatings.
Sodium Nitrite-Based Rust Preventative
These types are traditionally old powder formulations, although there are some liquid formulations out there, too. They were the original non-oil based rust preventatives on the market. They are very inexpensive and provide moderate to good corrosion protection when dried properly. Drying is a key part to these R.P.’s, since they are water soluble, to effectively work the product needs dried to touch. If the coating is allowed to dampen after drying (high humidity, extreme change of climate, etc), solid protection is unlikely. If all that is a required is a non-oily, moderate rust preventative, this may be an option. The film left on the part sometimes can be welded without causing issues. Their R.P. coatings can be removed with a mild alkaline cleaner.
Amine-Based Rust Preventative
These are some of the more modern options for non-petroleum rust preventatives. There are several amine sources for these products, included but not limited to triethanolamine and ethanolamine. They are typically liquid products, and work at various concentrations; some as high as 20% or as low as 3%. As with the sodium nitrite-based products, the amine-based R.P.’s must be completely dried and remain dry for maximum corrosion protection. Many of these products are use pre-welding applications without issue. They too can be removed via a mild alkaline cleaner. Some have been known to provide excellent corrosion protection lasting 60 to 120 days in open air, plant environments during Midwestern summer months.