Fasteners - hdgasa

Galfan coated wiresolution is used at 35°C. Thisprocess simulates exposure of thespecimens for up to 1000 hours,to an aggressive marineenvironment. Test results havesubstantiated the assumptionsthat Galfan’s corrosion resistanceprogressively improves over time.(b) Kesternich Test: The Kesternichtest is also based on exposureuntil a state of 5% Red Rust isreached. In this case a sulphurdioxide compound is used inaccordance with ASTM G1/88.Specimens are exposed in anatmosphere at 93 – 94% relativehumidity which contains 10% SO 2at 35°C. The graph belowillustrates the performance ofGalfan coating against Zinc.Ageing testsAgeing tests have demonstrated thatthe percentage of aluminium on theexternal surface of Galfan productsincreases with time. This developmentat the corrosion front, the decreasingof zinc and the increasing of thealuminium, connected to theincreasing of oxygen at the samelocations, becomes more pronouncedwith time.Following tests on exposure overtime in different environments theconcept of the Galfan PerformanceRatio (GPR) has been developed.GPR = Zinc loss for a heavyGalvanizing Coating / Zinc Loss for aGalfan CoatingResults have shown that GPR ≈ 2.0for 8.5 years and 3.0 for 25 years. Aprojection of this relationshipindicates that the GPR or 50 yearscould be ≈ 4.0.Standard coating thicknessesIn South Africa, the Zinc and Galfan(or Zinc-alloy) coating thicknessesset by SABS conform withinternational standards under EN10244-2. In this specification acoating thickness of 245g/m 2 isrequired for the Galfan coating on a2.7mm diameter steel wire (or0.035mm thick). SANS 1580 coversthe minimum coating thickness usingzinc only. For the same 2.7mm wirethis is at present 275g/m 2 (or 38µmthick).ConclusionsIn conditions of extreme exposure itis necessary to ensure that thecoating type is appropriate. In thepast zinc only coated wire wouldhave had to be carefully maintainedand at times replaced whenconditions were extremely severe.Now with the availability of Galfan,new opportunities have beenopened and the service life ofhydraulic structures especially, usinggabions and mattresses has beenimproved considerably. Users ofGalfan in certain parts of the worldhave stated that Galfan is capable ofproviding 4 to 5 times greaterprotection than zinc coating of thesame thickness.In addition to this it has been foundthat Galfan wire is easy to weave andits finish allows the cut ends of theselvedge to “heal over” thusproviding further resistance tocorrosion. Furthermore, Galfanmaintains a “like-new” appearanceuntil the end of its life span.Finally, Galfan allows the end user toachieve two important goals at thesame time: First, the provision of alonger corrosion life and second,considerably lower cost per year ofservice life.References1. Bergische Universitat GesamthoschschuleWuppera; 20002. Centre de Recherches Métallurgiques –Abbaye du Val-Benoit Liege: Belgium:19873. Nisshin Steel Company Ltd: 20004. J.L. Pagniez: French Coated SteelInformation Center: 19815. Mike Caroll: Davis Wire Corporation:20086. Alasdair Morrison; Cape Gate: 2011Prepared by Des Lange Pr Tech EngTechnical Manager: Maccaferri SA10 February 2011New Introductory GalvanizersInspection Course starting 2011This one day course has been designed to be moresimple and more practical than the current 2-day or thenew 3-day galvanizers inspectors course discussedelsewhere in this magazine.Topics to be covered and discussed are:• Brief description about corrosion• How zinc protects• The hot dip galvanizing process• Inspection before and after hot dip galvanizing• Multiple choice question test for course effectiveness.Should you require some background information on hot dipgalvanizing and its acceptance and have a limited formal education,this course is for you! Contact our offices for more details.30 Hot Dip Galvanizing Today Volume 8 Issue 1 2011