Soiled façades are cleaned cur­rent­ly with blast­ing pro­cess­es using water or mix­tures of water, air and solid blast­ing agents (e.g. sand, glass beads or cal­ci­um car­bon­ate). An al­ter­na­tive to the men­tioned clean­ing pro­ce­dures is of­fered by the plas­ma tech­nol­o­gy. Typ­i­cal façades ma­te­ri­als like clink­er, sand­stone, stoneware, mar­ble, gran­ite, an­odized alu­mini­um and stain­less steel can be cleaned with cold at­mo­spher­ic pres­sure plas­ma, as shown in the fi­nal­ized re­search pro­ject. Here­with was de­vel­oped a mo­bile wa­ter- and chem­i­cal free clean­ing method which has been proved to be also ma­te­ri­al pro­tec­tive.

As ubiq­ui­tous soils were used graf­fi­ti (acrylic and syn­thet­ic resin paint) and ar­ti­fi­cial at­mo­spher­ic soils. After soil­ing the sam­ples were ex­posed 30 days to an ar­ti­fi­cial weath­er­ing pro­ce­dure con­sist­ing of al­ter­nat­ing UV-ir­ra­di­a­tion and thaw­ing steps.

In order to achieve a high soil re­moval by means of plas­ma, dif­fer­ent pro­cess gases, like com­pressed air, argon and ni­tro­gen, were con­sid­ered and dif­fer­ent plas­ma pa­ram­e­ters, like noz­zle ge­om­e­try, dis­tance noz­zle to sur­face and num­ber of treat­ments, were var­ied.

An ef­fec­tive re­moval (up to 100 %) of acrylic and syn­thet­ic resin paints (black, green and red), as well as of algae and fungi was achieved by using a high­ly en­er­get­ic air plas­ma beam under spe­cial pa­ram­e­ter set­tings. White and sil­ver acrylic paints in­stead could be re­moved to a much lower ex­tend (max. 70 %). Nei­ther abra­sion nor ther­mal dam­age of the anal­ysed façade ma­te­ri­als could be de­tect­ed. Dur­ing the plas­ma treat­ment were reached rel­a­tive­ly low sur­face tem­per­a­tures de­pend­ing on the type of ma­te­ri­al con­sid­ered. Thus were mea­sured 60 to 80°C for min­er­al, re­spec­tive­ly 70 to 115 °C for metal­lic sub­strates.

The de­vel­oped plas­ma clean­ing method was eval­u­at­ed in prac­tice by com­par­i­son with con­ven­tion­al clean­ing meth­ods, in­clud­ing clean­ing agents. Con­trary to the water high pres­sure blast­ing method, all typ­i­cal soils (like paints, algae, fungi) could be re­moved by air plas­ma even from very rough façade ma­te­ri­als, like fin­ery and red clink­er, chem­i­cal- and residue-free.

The IGF-pro­ject 15271 N of the re­search as­so­ci­a­tion Europäische Forschungs­ge­mein­schaft Reini­gungs- und Hy­gien­etech­nolo­gie e.V., Cam­pus Ficht­en­hain 11, D-47807 Krefeld, was sup­port­ed via the AiF with­in the fund­ing pro­gramme „In­dus­trielle Gemein­schafts­forschung und –en­twick­lung (IGF)“ by the Fed­er­al Min­istry of Eco­nom­ic Af­fairs and Tech­nol­o­gy (BMWi) due to a de­ci­sion of the Ger­man Par­lia­ment..

The re­search re­port is avail­able on re­quest from FRT.