Log In. I should have read it over before clicking the "submit post" button. Edstainless, I agree that copper could be considered, although the potential for unsightly staining from the initial corrosion of the copper should be considered, too. Some homes in our area have bad discoloration of concrete from water running off copper roof components. RE: galvanized flashing against concrete This is a simple z flashing over the rim joist to under the concrete.
Register now while it's still Aluminum flashing corrosion concrete Not sure what pH Aluminum flashing corrosion concrete moisture between the flashing and wood. Membranes designed for use as waterproofing materials can have asphalts with lower softening points, and the asphalt can flow off the backing film in the hot environment within an exterior wall. The thermal-sprayed zinc will have different characteristics than galvanizing, but since galvanized coatings are also zinc the article may be a general indicator of performance. The wall cavity must not be blocked with mortar droppings, and the flashings and weeps must be very well constructed at these locations. These membranes are flexible and can be formed around many penetrations. Chemical resistance of the organic finishes is sufficient to withstand the mild cleaners acid or alkaline or other corrosives associated with the construction process or cleanup. For example, steel nails will rapidly corrode Black silky panties stories used to fasten copper flashing. Copper vs. These metals have unique abilities in that they can be formed and soldered in the field and will not corrode excessively under normal circumstances.
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Masonry Restoration: Brick, Stone, and Sometimes, masonry ledges or Aluminum flashing corrosion concrete elements often referred to as water tables deflected water off the fa?? Join Us! Preventing water leakage through masonry fa?? Guess anything is possible with the process of smelting lead but have you ever heard of poor quality control or lead that was Aluminum flashing corrosion concrete with impurities that would A,uminum premature corrosion? Drips Drips are important because they divert water away from the surface of the wall see Figure 1. In general, aluminum flashing is not recommended for direct contact Aluminuum pressure-treated lumber. Galvanic Corrosion With metal flashing, roofing, or any metal building components, the safest strategy is not to mix metals that come in direct contact with one another. If this is in a location that can be exposed to road salt northern or ground salt coastal then SS is not a good choice. So — I am very appreciative of your detailed response. This reaction reduces the pH of the pore solution to as low as corrksion. Any suggestions on a piece of metal this shape, that I can find at a normal hardware store Aluminum flashing corrosion concrete order easily online? Such additives serve as one of the best ways to control flash corrosion. Assuming that the flashing is or gauge G steel, a reasonable guestimate is 20 years of service life for the steel flashing, maybe less because of corroeion proximity to salt water. As such, they can also flashjng as load-bearing walls.
Masonry wall flashings Get masonry industry news in your inbox Subscribe to Masonry Messenger to receive the masonry resources and information you need to stay current.
- The thin aluminum flashing widely used today is inexpensive, but is a poor choice in many applications.
- Flash corrosion is the general and rapid corrosion that instantly occurs when metals are exposed to corrosive environments.
- Corrosion of reinforcing steel and other embedded metals is the leading cause of deterioration inconcrete.
- Preventing water leakage through masonry fa??
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- Aluminum is actually very prone to corrosion.
Architectural aluminum is widely used for window and door frames because it is attractive, durable, and requires little maintenance see Fig. However, unprotected aluminum interacts with cement-based materials, sometimes resulting in severe frame damage. This article provides guidance for protecting aluminum frames from mortar used in masonry walls.
In fresh concrete, aluminum reacts principally with alkali hydroxides from cement. The pH of fresh mortar ranges from 12 to Aluminum in contact with plain concrete can corrode, and the situation is worse if the concrete contains calcium chloride as an admixture or if the aluminum is in contact with a dissimilar metal. Ensuring a good quality installation of aluminum-framed windows and doors includes proper material selection and correct construction practices. The American Architectural Manufacturers Association recommends using only coated windows for installations involving any cement-based materials, including masonry.
The coating materials may be either organic, such as paint, or inorganic, such as anodized aluminum. Currently, organic-type coatings are the most widely used finishes for architectural aluminum. For exterior use, the AAMA recommends high-performance coatings fluorocarbons, siliconized acrylics, siliconized polyesters that are capable of weathering outdoor exposure for at least 20 years.
Some coatings are only able to protect up to a pH of about Fresh mortar can stain frames coated with these materials, and if allowed to rest on the frame, the mortar can also lead to corrosion or other surface damage. To prevent this, fresh mortar droppings should be removed as quickly as possible from aluminum frames.
Organic coatings on extruded aluminum window and door frames are categorized as pigmented, high performance, and superior performing coatings. For light commercial and residential applications, the "pigmented" category is acceptable. The coating should be at least 20 microns thick. Chemical resistance of the organic finishes is sufficient to withstand the mild cleaners acid or alkaline or other corrosives associated with the construction process or cleanup. AAMA Standards , , and provide test methods and performance criteria including chemical resistance and corrosion resistance for pigmented, high performance, and superior performing organic coatings, respectively.
Inorganic coatings, such as anodized finishes, convert the outer layer of aluminum to aluminum oxide, producing an extremely durable surface. Applying a clear organic coating can further protect the anodized surface. To prevent staining, alkaline building materials such as wet mortar, plaster, or concrete should be removed quickly from anodized surfaces. Masonry walls should be built well in advance of inserting frames into the wall to protect aluminum. This allows time for the mortar to cure and dry, which reduces the movement of alkalies.
The frame is then attached with screws at the bottom, top, and sides see Fig. Even so, new hardened mortar that is rewetted by precipitation can still be a source of alkalies.
Good coatings should adequately protect aluminum from chemical attack. Two coats of bituminous paint or zinc chromate primer are often used in severe applications to provide separation of the aluminum from the cement-based products. A light coating of petroleum jelly painted onto the surface of the frame is another way to provide temporary protection to the finish during construction.
Anything that directs moisture away from the frame reduces alkali exposure. Therefore, if it is possible to separate the frame from direct contact with the mortar by a sheet material flashing , this can help reduce corrosion as well.
Plastics, rubbers, and vinyl materials resistant to UV degradation and attack by alkalies are all acceptable. If the masonry wall is to be cleaned following construction, the aluminum must not be subjected to harsh chemicals and must be rinsed thoroughly.
Clear water should remove any products used to clean the wall and any alkalies washed off the building face. For specifications and other information on aluminum coatings, visit American Architectural Manufacturers Association. Cement Industry Annual Yearbook U. Greg Halsted, P. Joshua Gilman, P. Aluminum Frames in Masonry Walls. Aluminum frames make attractive windows and doors in masonry buildings.
Inset shows a close-up of a joint filled with caulk between the frame and masonry wall. Materials This cut-away section of a masonry wall is a typical construction detail, which includes a gap for caulk all around the frame. Construction Masonry walls should be built well in advance of inserting frames into the wall to protect aluminum. Place aluminum frames into walls after mortar has cured. Separate frame and masonry with a caulk gap.
Remove fresh mortar from aluminum frames as quickly as possible. Direct water away from the wall with drips and flashings.
The mortar can harden and block the flow of water out of the weeps. Copper vs. Existing questions. Flashings at these locations should have an upturned back leg to prevent water from flowing off the back of the flashing. Water is required for corrosion, so the longer this area stays wet, the more rapid any corrosion will be. Window and door heads Flashings at window heads are very similar to those at shelf angles.
Aluminum flashing corrosion concrete. Report Abuse
The flashing will be 16" cut by 24'. There will be an L flashing on top of the concrete as well. Thanks Jeff RE: galvanized flashing against concrete I would avoid stainless if salting is common.
It is highly likely to pit in the crevice areas and will be quite expensive relative to other options. Aluminum may not be much better in some cases. I've seen yr. ASM Metals Handbook indicates that aluminum in contact with fresh concrete may undergo some superficial etching from the high pH, but that the long term effect is oftem minimal. It does also say that aluminum components such as highway poles and railings in contact with concrete in crevice areas where salts may accumulate are often coated witha sealing compound to minimize salt getting into the crevices.
It further says that aluminum alloys of 2XXX series and 7xxx series are less resistant to chloride pitting than alloys of the 3xxx, 5xxx and 6xxx series, with the 6xxx being the least preferred of the three choices. Typical seawater penetration rates are reportedly less than 0. Sounds like someone needs to invent and distribute some type of nonmetallic flashing if you want relaible yr protection.
RE: galvanized flashing against concrete The copper that I have seen installed was pre-washed with acid to generate the patina and minimize the staining. I agree, don't use stainless. There are two problems with galvanized.
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Home Forums Materials Engineers Activities Corrosion engineering Forum galvanized flashing against concrete thread I say stainless because I believe in time galvanized steel will deteriorate as would aluminum. Any official advice would be appreciated. I am not a structural guy with formal experience in the building industry, but I believe that galvanized steel components are very commonly used as anchors for typing wood to concrete as well as for many similar applications.
Stainless steel is not impervious to corrosion in crevice conditions. The suscpetibility to corrosion will be related to how tight the corrosion, exposure time to water, whether the wood is treated with anything that promotes pitting of stainless, etc.. The corrosion rate for galvanized coatings exposed to water is reportedly the lowest in the pH range of Not sure what pH the moisture between the flashing and wood.
Unlike aluminum oxide, the expanding and flaking off of rust exposes new metal to further rusting. This is why it is so important to provide a barrier so rust doesn't start. While aluminium doesn't rust, it often becomes dull from corrosion, and is often encrusted with brake dust, calcium, lime, tarnish, grease, oil and hard water stains.
Simply washing it off will not work, you need something stronger and more effective to do the job. We recommend Flitz Aluminum Pre-Clean to remove the surface grime, corrosion and buildup followed by Flitz polish paste or liquid to restore a brilliant shine. Does Aluminum Rust? Aluminum corrodes but it does not rust. Rust refers only to iron and steel corrosion. Related Items.
The thin aluminum flashing widely used today is inexpensive, but is a poor choice in many applications. Also choose flashings that will last at least as long as the siding or roofing materials where they are to be placed. When incompatible metals are in direct contact, and the materials remain wet, the more active metal corrodes and the passive metal is protected see The Galvanic Scale , below. However, the aluminum alloy commonly used in flashings tends to pit and oxidize and pit in salty or polluted air.
Unpainted aluminum flashing will also corrode in contact with pressure-treated wood, concrete, mortar, or other alkaline masonry materials. Also aluminum cannot be soldered, limiting it to simple profiles. If using aluminum, use at least. Some home center coil stock is. Choose prefinished stock for difficult environments such as urban areas with air pollution, as these are much more resistant to corrosion. However, cut edges are still vulnerable. Also be aware that the actual thickness is less than the nominal thickness on pre-painted stock.
In coastal areas,. Copper flashings are a good choice for many applications, but expensive. Two types are available: soft and cold-rolled. Copper flashing thickness is rated by oz. Nails in contact with the copper should be copper or stainless steel. Over time, all unpainted copper will oxidize and develop a green patina that protects the underlying copper.
While most people find the patina attractive, the runoff of the oxidation can leave streaks of blue-green stains on the siding or trim. Some experts caution against using copper or lead-coated copper in contact with red cedar or redwood or rainwater that drains over the wood.
Over time, the copper surface will be etched by the acidic wood runoff. The combination of acidic rain and exposure to runoff from red cedar is suspected as the cause. Lead-Coated Copper. Lead-coated copper has a less noticeable gray runoff. Also, copper flashing will react in contact with galvanized steel unless the copper is lead-coated.
For special flashing applications where a high degree of malleability is required, such as chimney step flashing, lead is a good option. Lead is easy to bend and mold, and is very resistant to corrosion. Lead is relatively soft, however; so it should not be used where it will be bumped or walked on. Also, it is best to leave lead flashings unfastened on one side to allow movement.
If pinned on all sides, the flashing can fatigue and tear due to thermal movement. Galvanized Steel. This is the least expensive and least durable metal flashing material.
It is not recommended in harsh climates or in contact with masonry materials or pressure treated wood. Like other galvanized products, the galvanic coating will eventually wear away exposing the underlying steel to corrosion. A proprietary version called Galvalume has a much longer service life, but is still not recommended for contact with masonry or treated wood. With metal flashing, roofing, or any metal building components, the safest strategy is not to mix metals that come in direct contact with one another.
Use aluminum flashing and fasteners in contact with aluminum, copper flashing and copper nails with copper roofing, gutters, etc. When this is not possible, choose a second metal that is not likely to lead to galvanic corrosion or use a physical barrier to separate the two metals. The Galvanic Scale. Metals at the top of the chart are called anodic, or active, and are prone to corrode; metals at the bottom are cathodic, or passive, and rarely corrode.
The farther apart two metals are on the chart, the greater their tendency to react and cause corrosion in the more active metal. Metals close to each other on the scale are usually safe to use together. The Area Effect. The rate of corrosion is controlled by the area of the more passive metal. For example, a galvanized steel nail active will corrode quickly if surrounded by a large area of copper flashing passive.
If a copper nail is used in galvanized steel flashing, however, the corrosion of the steel will be slow and spread over a large area, so it may not be noticeable. In each case, the active metal corrodes, and the passive metal is protected. In addition to galvanic corrosion, a number of other common building materials can harm the finishes on metal flashing or lead to etching or corrosion of the material itself:.
Wet Mortar. Aluminum flashing materials can be damaged by alkali solutions such as wet mortar. Where contact with wet mortar cannot be avoided, one option is to spray the metal with lacquer or a clear acrylic coating to protect it until the mortar is dry.
Pressure-Treated Wood. Contact with the wood can cause corrosion in both aluminum and galvanized steel. Another good option is membrane-type flashing, used alone or as a layer to separate the pressure-treated wood from the metal flashing or steel framing connectors.
Other options, although more expensive, include stainless-steel the best choice for coastal projects , copper, and lead. Plastic flashings made from PVC and other plastics are safe to use, but may not be as durable as metal in most applications. Salt Spray. Saltwater spray is very hard on steel and uncoated aluminum products and may lead to corrosion within 5 to 7 years.
I have lead chimney flashing that is corroding less than 3 years after installation. The step flashing underneath is aluminum. The aluminum appears to be in same condition as when installed. The lead flashing looks fine on the vertical portion of the chimney but has turned white and shows pitting and significant deterioration on the sloped portions atop the asphalt shingles. We live in the northeast and burn firewood in a wood stove which vents out this chimney. Any thoughts on the source of the lead corrosion and how to prevent this from happening again?
Lead is a very stable, non-reactive metal, so this is a bit of a mystery. Lead, or the run-off from lead, can cause corrosion in aluminum under some conditions, but aluminum should not harm lead. Where the lead has turned white, this is a natural patina of lead carbonate caused by the reaction of lead with carbon dioxide in the air.
This white film builds up over time and protects the underlying lead from further damage. Condensation on the bottom face of lead flashing can lead to deterioration since the protective carbonate layer is unlikely to form on the bottom surface.
However, in your case, it sounds like the corrosion is on the top surface of the lead. While lead flashing is very common on older chimneys, and usually lasts for decades, under some conditions concrete or mortar made with Portland cement can harm lead.
The strong alkaline solution created by the wet concrete mix can attack lead even after the concrete or mortar has cured, since some moisture remains in pores of the concrete or mortar. This is generally a problem when the lead is embedded in concrete or mortar. Another possible culprit is air pollution, if you are in an urban area. Air pollution accelerates the deterioration of nearly all building materials. Start by thoroughly cleaning the lead surface, then prime with a metal primer made for non-ferrous metals, followed by a topcoat made for metal or multi-surfaces.
This should protect the lead surface from direct contact with anything that could be promoting corrosion. You could also try switching to copper, although it may not be any better than the lead you are currently using. In fact, copper flashing is often coated with lead to make it less reactive with galvanized steel. You can read about the effects of concrete on lead and other metals in this article from Concrete Construction magazine.
I believe your conclusion regarding the cause is correct. The areas of the chimney that were flashed with the same lead, but are not below a mortar joint, look like new. This appears to correlate to your hypothesis. Unfortunately the deterioration of the much of the lead flashing is to the point that replacement is necessary and coating with a paint a bit too late.
Lead flashing on chimneys needs to be embedded into the mortar in order to be create a watertight joint. Wondering if there is possibility I purchased a bad batch of lead or used the wrong mortar? Guess anything is possible with the process of smelting lead but have you ever heard of poor quality control or lead that was contaminated with impurities that would induce premature corrosion?
I agree with you that lead or copper is the material of choice for chimney flashing. I am also puzzled by its failure in three years. I would suggest buying from a contractor lumberyard or masonry supply house rather than a home center. Home centers have many perfectly good products at good prices, but some are poor quality. When you replace the flashing, I would recommend sealing the embedded the flange with sealant rather than mortar.
Polyurethane sealant is pretty messy and difficult to tool, so best to practice first on a test joint — and wear gloves. Sealing the mortar might also help. The only type of sealant you should use on masonry brick, mortar, concrete is silane or siloxane, or a mix of these.
They will limit the intrusion of moisture into the mortar and are usually used to protect the mortar. In your case, sealing may also help protect the flashing if the cause is alkaline water leaching out of the masonry. Many years ago a friend of mine got third-degree burns on both knees from kneeling on wet concrete for a few hours while finishing a slab. This drove home to me the corrosive power of wet Portland cement. I always wear rubber gloves and other protective gear when working with concrete or mortar.