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RWEATHER AND CORROSIONE SISTT A NKalzip ® – proven to last, whateverKalzip aluminium standing seamroofing and wall cladding hasrevolutionised the design of buildingenvelopes, making possible someof the world’s most dramaticarchitecture. But perhaps even moreimportant is its inherent durability,delivering virtually maintenance-freeperformance for decade after decade.40 years’ exposure andstill performing.The latest findings of a long-termproject by German technical researchbody BAM (Federal Institute forMaterials Research and Testing)show that, even after 40 years’exposure to potentially corrosiveindustrial pollutants and atmosphericattack, the base material of a Kalziproof – and therefore its ability toperform – remains fully functional.Aluminium is inherently durable and weatherresistant,creating an inert, hard oxide layerthat resists most pollutants and ‘regeneratesif cut or scratched. With Kalzip, an additionalweathering layer of bespoke alloy furtherimproves this resistance to corrosion, resultingin a BBA-certified life expectancy in excessof 40 years.Experience suggests this to be a conservativeestimate – Kalzip roofs have already exceededthat life expectancy – and the findings of theBAM report confirm this.The research undertaken by BAM investigatedthe condition of roof samples taken frombuildings in three locations, selected for theirdifferent atmospheric conditions and the threatsthat these present, e.g. humidity, rainfall, attackby chemical pollution, UV radiation etc.And the results clearly show that the Kalzipaluminium roofing tested remains in goodworking order, 40 years or more from the dayit was first installed. This document providesa summary of the findings published in BAM-TestCertificate VI.1/14669.Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5
Wthe conditionsPacking Hall, HamburgCongress Hall, NurembergStorage Facility, EssenNaCl CO 2CO HC1SO 2This plated aluminium Kalzip roof, at apacking hall in the Freeport of Hamburg,was installed in 1970. While its locationis classed as an urban climate, the hallis actually situated in the harbour area,a marine environment where sodiumchloride is the major atmospheric pollutant.Tests carried out on a storage hall atHamburg’s container terminal in 1972(Fig. 1, after 1 years’ exposure), showedearly signs of pitting corrosion; similar tests21 years later (Fig. 2) showed further pitting,but still no damage to the core material.While the 2009 samples were takenfrom a different structure, they are stillrepresentative in terms of age andatmospheric exposure conditions. The firstsample (Fig. 3) was taken from an area ofthe eaves and shows further increase incorrosion, both on the inner and the outerside. The second (Fig. 4), taken from themiddle of the roof, shows similar corrosionto the outer side but limited damage to theinner side.Again, pitting and corrosion is restrictedto the protective layer; the bulk materialremains completely unaffected.BAM expert opinionAfter 40 years of exposure, the bulk materialis not yet affected… At the present momentthe function of the roof is completely in agood condition.The Kalzip roof on Congress Hall,Nuremberg was installed in 1968.The climate in this location is a mixtureof urban and rural and the main pollutantsare carbon monoxide and carbon dioxide,neither of which has any major effecton aluminium.Initial tests carried out in 1993 (Fig. 5)showed that pitting corrosion was restrictedto the plating layer and did not extend tothe underlying bulk material.In 2009, three further samples were taken,allowing assessment of the roof after 41years’ exposure. The first two samples(Fig. 6 and Fig. 7) were taken from eavesadjacent to the earlier tests and pittingcorrosion remains limited to the platinglayer. The third sample (Fig. 8) was takenfrom a seam and the protected inner sideof the sheet shows no sign of corrosion.The freely weathered upper side showspitting typical for this location, none ofwhich reaches the bulk material.So, in every sample taken, the weatheringlayer – designed to protect the purer basematerial – continues to do its job.BAM expert opinionThe pitting corrosion effects in the platinglayer detected in the cross section stop atthe bulk material and thus do not affectthe function of the roofing after 41 yearsof use… long durability can be expected.Testing at the third location, Essen, wascarried out on a roof at a metal storagefacility erected in 1974. The climate at thisinstallation is classified as industrial, wherethe most frequently encountered pollutantsare sulphur dioxide and hydrogen chloride.Tests in 1972 and 1993 were carried outon a different building, also in Essen, butaccess was no longer possible. While theEssen location is the same, there is aneight year age difference between the twobuildings tested so a direct comparisonis not possible.The first sample (Fig. 9) was taken fromthe eaves of the storage facility; while pittingto the plating layer is apparent on bothsides, the core material remains unaffected;the second sample (Fig. 10), taken from themiddle of the roof, shows pitting to theoutside but only very limited damage to theinside, neither affecting the bulk material.BAM expert opinionThe investigations reveal numerouscorrosion effects which, however, do notextend to the bulk material.Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10
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