Galvanized roofs

AGSCO has determined that they stand to lose over a billion dollars if the claim is true. They have come to I.O.N.S. and have asked us to take a look at galvanized steel samples from both the galvanized sheet metal stock purchased by Titanic and also a batch of galvanized roofing nails manufactured at about the same time. They want us to determine the amount of zinc coating on the steel. They would like us to report the results both in percent zinc and also in grams of zinc per cm2 of steel. They want us to measure both the sheet metal and the nails, since if there is a problem with the sheet metal, then there also may be a problem with the nails, since they were manufactured at about the same time. 

Figure 6.25 Section of galvanized roof panel after five years under PFRI.

All of the general t5 es of corrosion attack occur in the atmosphere. Since the corroding metal is not bathed in large quantities of electrolyte, most atmospheric corrosion operates in highly localized corrosion cells, sometimes producing patterns difficult to explain as in the example of the rusting galvanized roof shown in Fig. 9.1. 

Figure 9.1 Rusting galvanized roof with regular bands of rust.

The application of zino within the last twelve years has been very much extended, not only for use in brass foundries, but in several other departments, such as in galvanizing iron for light roofing and for fencing, and in fact for all the lighter kinds of iron which have to be exposed to the air for the base of electro-plated articles, for paint, and various other applications. 

Because of the unusual amount of dust deposited and because the dust came from an area that has received heavy annual treatment with pesticides for many years, a large sample was collected for analysis at an installation that had previously been used to collect rainfall. Essentially, the collection surface is one fourth of a galvanized iron roof with the gutter arranged to discharge roof runoff into a collection tank. The collection area is 1090 square feet calculated from a horizontal projection. The day after the storm, the roof surface was flushed with 110 liters of Cincinnati tap water, and the dust slurry was collected in a stainless steel tank. The roof surface had been cleansed before the dust was de-... 

Materials. The type of material used for roof and down conductors seems to be governed by tradition. Copper, aluminum and galvanized steel are all acceptable but there are conflicting opinions as to whether the material should be of rod, tube, strip or stranded form. Stranded copper is not deemed acceptable in the codes of several countries, although it is accepted in the USA code. Copper or copper alloys must not be used on a building with aluminum fittings. 

The trigger is made from galvanized tin. A slot is punched in the trigger flap to hold a roofing nail, which is wired or soldered onto the flap. The trigger is bent and nailed to the stock on both sides. 

The API 521 also states that "it is essential that persormel within the restricted area have immediate access to thermal radiation shielding or protective apparel suitable for escape to a safe location." Radiation shields are structures sometimes located near the base of the flare sfack designed wifh a galvanized or reflective steel roof. Some planfs design a roofed corridor that leads from fhe base of fhe sfack to a safe location away from high radiation levels. 

Many studies report that the age of the home is a chief predictor of Pb concentration in household dust, largely due to the prevalence of Pb-based paint in older homes (Sutton etal., 1995 Rasmussen etal., 2001 Adgate etal., 1998 Davies etal., 1990 Thornton etal., 1994 Meyer etal., 1999). Older paints had concentrations of up to 50% Pb, while later paints had lower Pb concentrations but increased concentrations of Ti, Zn and Ba (U.S. EPA, 1986). Thus, indoor Pb levels tend to increase while houses are being renovated, particularly if the renovation involves electric sanding or burning with a blow lamp (Laxen etal., 1988 Davies etal., 1990). Galvanized iron roofing material, used commonly in Australia and New Zealand, con-... 

Figure 11. Roof pins reinforcing a lichen-covered asbestos-cement roof by means of zinc-galvanized plates. Note the lichen desert (arrows) delineated by a water dripping pattern. Moshav Herulh, Israel, May, 1988.

Figure 13. Toxic effect of Zn-ions (arrows) on epilithic crustose lichens and mosses. The Zn ions derive from galvanized plates and objects fixed to the roof. Laerdalsoyri, Norway. Summer, 1992.

The detrimental effect of both Zn and Pb on lichens is well known. Dissolved zinc ions from galvanized barbed wires (Seaward, 1974), roof fixtures (Garty et al., 1979) and fences (Plummer, 1982) are very toxic to lichens. Zinc ions lead to the elimination of lichens from different substrates such as wooden poles (Fig. 10), various constructions made of concrete or asbestos-cement (Figs. 11 and 12) and roof tiles (Fig. 13). 

Flashing - Metal, usually galvanized sheet metal, used to provide protection against infiltration of precipitation into a roof or exterior wall usually placed around roof penetrations such as chimneys. 

Roof Ventilator - A stationary or rotating vent used to ventilate attics or cathedral ceilings usually made of galvanized steel, or polypropylene. 

The galvanizing industry in the United States is divided into two classes namely, fabrication and sheet galvanizing. The fabrication business deals with stmctural components such as piping, I-beams, poles, handrails, and other heavy duty products. The sheet business deals with galvanized sheet metal for equipment, roofing, panels, and other nonstructural steel applications. 

Design (avoidance of dissimilar metals, galvanic couples, improper materials, high fluid velocities in inappropriate places, caulking or seal welding of areas prone to crevice corrosion, roof design, etc.)... 

Copolymers of vinylidene fluoride with tetrafluoroethylene or hexafluoropropy-lene have recently been developed as an air-drying paint mainly for repair coating of the PVDF finish [2.19]-[2.21], Poly(vinylidene fluoride) is now widely used for coil coating of galvanized iron and aluminum sheets, and as a maintenance-free coating for walls of skyscraper buildings and roofing of industrial constructions. 

Buses have a profiled steel framework that is clad on the sidewalls and roof with steel, galvanized steel, and aluminum alloys. The anticorrosive primer must therefore adhere well to all of these metals, and to glass-fiber-reinforced plastics. 

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