This post is written by my colleague Warren Brand. Warren is a certified NACE III coatings consultant with his company Chicago Coatings Group. You can contact him here for professional specification and coating review, coating system design, and failure analysis.
The inevitable forces of winter bring with it a fresh set of challenges to those tasked with the upkeep of all structures. Rust (corrosion) can be severely damaging and have lasting negative effects. It is crucial that everyone from building owner, engineer or homeowner be able to accurately recognize and effectively reduce the corrosion of a building or other surface.
Below are tips for identifying corrosion and the key steps that can be utilized as a “stop-gap” for the winter, if proper coating measures are not possible.
Corrosion, in most cases, is pretty obvious. Since most things that corrode are made of steel (iron) the corrosive product (as we call it in the business) is iron oxide, bright, red rust. When steel rusts, it expands at an incredible rate. Because of this, there are three main ways in which identifying the corrosion becomes possible:
- See the rust.
- See the results of the rust in terms of streaking or staining from rust, like on the side of a building, under a gutter or at bridges.
- See the results of hidden rust.
The first two observations can be made by the untrained eye fairly simply, since most of us know what rust or streaking of rust looks like. However, hidden rust can be challenging to point out.
This is generally seen in concrete, where rebar has started to rust and begins to push away the concrete. Rust expands very powerfully and once the rebar starts rusting, even up to six inches into solid concrete, it will eventually push and damage the concrete. The key here is, if there is staining or bulging of concrete for no apparent reason, then there is a reasonable expectation of hidden rust.
Aside from concrete, aluminum is one other source where corrosion can prove much more difficult to observe. Aluminum, in general, perfumes very well against corrosion. However when it corrodes, its byproduct is aluminum oxide, which is white and powdery.
Personal Example about Hidden Rusting: I have 6 iron chairs in my backyard that are about 12 years old. They are powdered coated (a type of paint system) but where the water collects at the edges of the seats, the chairs began to rust. I couldn’t see the rust because it was hidden beneath a lip of the chair. I only found this out after one of the chair basis broke. I immediately turned all of the other chairs over and checked them, and sure enough, they were all rusted.
Properly painting a substance that is obviously rusting is the ideal situation. However, there are times where it is too cold, time is short or it is impossible to prepare the surface properly. In these moments, there are a few options to buy time until the job can be addressed properly.
Before diving into choosing a “stop-gap”, make sure that whatever the corrosion issue is, it is not critical or immediately dangerous to life or health (IDLH). It is not an appropriate option to use a stop-gap measure in certain circumstances, such as a leaking and rusted gas tank or supporting structure. Find a way to do that job completely and correctly, without putting it off.
If it is not a situation that is IDLH, then there are many products on the market that will do a surprisingly effective job of preventing rust. The best of the bunch is WD 40, which most are unaware stands for Water Displacement. WD 40 is a viable alternative for “cleaning” a surface as long as all safety precautions are followed. After applying WD 40 to help prepare the surface, there are a few materials that can be used to bide time for the rusting area:
- Vaseline and Mineral Oil – These may be hard to cleanly remove later once properly applying paint, but can do the job for now.
- Caulk – Find a cold-cure caulk, squeeze it out on the surface and use a gloved hand or firm brush to work it into the rusted areas.
- Olive/Vegetable Oil – These can be used in a pinch, not best case scenario, but effective nonetheless.
- Grease – Any type of grease can work, with Calcium Sulfonate grease being the best. This option can have similar removal issues as vaseline and mineral oil do.
- Candle Wax – DO NOT use where fire may be an issue. In other circumstances though, paraffin does a nice job mitigating rust issues.