Boden, M

Lambert, Paul

Lewis, Oliver

O'Flaherty, Fin

Stephenson, Dan

Thistlethwaite, S

English

Sheffield Hallam University Research Archive

A Study of Aluminium Zinc Indium Thermal Spray Coatings for the Protection of Steel Rebars in Reinforced ConcreteLEWIS, Oliver, O'FLAHERTY, Fin, LAMBERT, Paul, STEPHENSON, Dan, BODEN, M and THISTLETHWAITE, SAvailable from Sheffield Hallam University Research Archive (SHURA) at:http://shura.shu.ac.uk/5666/This document is the author deposited version.  You are advised to consult the publisher's version if you wish to cite from it.Published versionLEWIS, Oliver, O'FLAHERTY, Fin, LAMBERT, Paul, STEPHENSON, Dan, BODEN, M and THISTLETHWAITE, S (2011). A Study of Aluminium Zinc Indium Thermal Spray Coatings for the Protection of Steel Rebars in Reinforced Concrete. In: 5th RIPT (Les Recontres Internationales sur la Projection Themique), Limoges, France, 7-9 December 2011.Repository use policyCopyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in SHURA to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain.Sheffield Hallam University Research Archivehttp://shura.shu.ac.uk Experimental	  Procedure	  Concrete	  Blocks	  Concrete	  blocks	  measuring	  170	  x	  170	  x	  55	  mm	  were	  cast3	  with	  one	  of	  three	  surface	  ﬁnishes:	  •  Steel	  mould	  ﬁnish	  •  U4	  ﬂoat	  ﬁnish	  in	  accordance	  with	  MCHW	  14	  •  Grit	  blasted	  ﬁnish	  to	  BS	  EN	  17665	  Coa.ngs	  Commercially	  available	  aluminium	  zinc	  indium	  coaMngs	  (composiMon	  given	  in	  table	  1)	  were	  applied	  by	  arc	  spraying.	  	  	  CoaMngs	  with	  a	  nominal	  thickness	  of	  200	  and	  350	  µm	  were	  applied	  for	  comparison.	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  Tes.ng	  The	  ability	  of	  the	  coaMngs	  to	  sacriﬁcially	  protect	  steel	  rebars	  was	  studied	  by	  measuring	  the	  corrosion	  current	  using	  a	  zero	  resistance	  ammeter	  (ZRA).	  The	  experimental	  arrangement	  is	  shown	  in	  ﬁgure	  2.	  A	  1:1	  anode-­‐cathode	  raMo	  was	  used.	  	  AXer	  2	  weeks	  exposure	  to	  5%	  w/v	  sodium	  chloride	  soluMon,	  the	  adhesion	  of	  the	  coaMngs	  was	  determined	  by	  pull-­‐oﬀ	  tests	  using	  50	  mm	  diameter	  dollies	  a]ached	  to	  the	  surface	  (ﬁgure	  3).	  A	  minimum	  of	  two	  tests	  was	  performed	  on	  each	  sample.	  	  	  A	  Study	  of	  Aluminium	  Zinc	  Indium	  Thermal	  Spray	  Coa;ngs	  for	  the	  Protec;on	  of	  Steel	  Rebars	  in	  Reinforced	  Concrete	  	  O.	  Lewis1,	  F.	  O’Flaherty1,	  P.	  Lambert1,	  D.	  Stephenson2,	  M.	  Boden2	  and	  S.	  Thistlethwaite2	  1.	  Materials	  and	  Engineering	  Research	  Ins4tute,	  Sheﬃeld	  Hallam	  University,	  Howard	  Street,	  Sheﬃeld.	  S1	  1WB	  2.	  London	  and	  Scandinavian	  Metallurgical	  Ltd,	  Fullerton	  Road,	  Rotherham.	  S60	  1DL	  	  Background	  •  Steel	  reinforcement,	  or	  ‘rebars’	  are	  extensively	  used	  in	  concrete	  structures	  but	  are	  suscepMble	  to	  corrosion	  a]ack,	  leading	  to	  cracking	  and	  spalling	  of	  the	  concrete.	  	  •  MiMgaMon	  measures	  include	  modifying	  the	  internal	  environment	  in	  the	  concrete	  (e.g.	  chloride	  extracMon),	  adopMng	  cathodic	  protecMon,	  creaMng	  a	  barrier	  between	  the	  reinforcement	  and	  the	  concrete	  (i.e.	  coaMng	  the	  reinforcement)	  or	  using	  more	  corrosion	  resistant	  materials	  for	  the	  rebars1.	  	  •  A	  metallic,	  thermally	  sprayed	  coaMng,	  on	  the	  concrete	  surface	  can	  form	  a	  protecMve	  barrier,	  whilst	  also	  cathodically	  protecMng	  the	  rebars,	  provided	  an	  electrical	  connecMon	  is	  made	  to	  the	  coaMng.	  	  •  The	  beneﬁts	  of	  this	  method	  include	  the	  ability	  to	  deposit	  a	  diverse	  range	  of	  thick	  (up	  to	  around	  500	  µm)	  coaMngs	  which	  can	  also	  be	  repaired	  in-­‐situ2	  (ﬁgure	  1).	  Project	  Objec;ves	  •  Determine	  the	  ability	  of	  thermally	  sprayed	  Al-­‐Zn-­‐In	  coaMngs	  to	  sacriﬁcially	  protect	  steel	  rebars	  in	  a	  chloride	  environment.	  •  InvesMgate	  the	  eﬀect	  of	  surface	  ﬁnish	  on	  the	  bond	  strength	  of	  the	  coaMngs	  aXer	  exposure.	  Figure	  1	  Photograph	  Showing	  Applica;on	  of	  a	  Thermal	  Spray	  Coa;ng	  to	  a	  Concrete	  Structure	  (Photo	  courtesy	  MetallisaMon	  Ltd)	  Figure	  3	  Corrsion	  Current	  Data	  for	  (a)	  200	  micron	  and	  (b)	  350	  micron	  Al-­‐Zn-­‐In	  Coa;ngs	  in	  5%	  w/v	  NaCl	  Figure	  4	  Al-­‐Zn-­‐In	  Coa;ng	  Average	  Bond	  Strength	  Data	  AYer	  2	  Weeks	  Exposure	  in	  5%	  w/v	  NaCl	  Zinc	   Indium	   Aluminium	  ComposiMon	  (wt%)	   4.5-­‐5.5	   0.02-­‐0.05	   Remainder	  Table	  1	  Nominal	  Composi;on	  of	  Al-­‐Zn-­‐In	  Coa;ng	  Concrete	  Block	  Al-­‐Zn-­‐In	  CoaMng	  Steel	  Panel	  5%	  w/v	  NaCl	  ZRA	  Figure	  2	  Schema;c	  Showing	  Experimental	  Arrangement	  Used	  for	  Zero	  Resistance	  Ammetry	  Tes;ng	  Figure	  3	  Photographs	  Showing	  Pull-­‐oﬀ	  Bond	  Tests	  Results	  Conclusions	  •  Thermally	  sprayed	  Al-­‐Zn-­‐In	  coaMngs	  are	  able	  to	  cathodically	  protect	  steel	  rebars.	  •  Post-­‐exposure	  coaMng	  adhesion	  is	  be]er	  on	  grit	  blasted	  surfaces.	  •  Increasing	  coaMng	  thickness	  has	  a	  negaMve	  eﬀect	  on	  bond	  strength.	  Further	  Work	  •  Further	  ZRA	  tests	  and	  pull-­‐oﬀ	  bond	  tests	  of	  diﬀerent	  coaMngs	  thicknesses	  and	  surface	  ﬁnishes.	  •  DepolarizaMon	  tests	  in	  chloride	  soluMon.	  •  ComparaMve	  trials	  with	  pure	  aluminium	  coaMngs.	  1.	  P.R.	  Roberge,	  ‘Corrosion	  Engineering:	  Principles	  and	  Prac4ce’,	  McGraw-­‐Hill	  2008	  (1st	  ed.)W.E.	  Ballard,	  'Metal	  Spraying	  and	  the	  Flame	  Deposi4on	  of	  Ceramics	  and	  Plas4cs',	  Charles	  Griﬃn	  1963	  (4th	  ed.)	  2.	  K.	  Baldwin,	  R.I.	  Bates,	  R.D.	  Arnell	  and	  C.J.E.	  Smith,	  Corrosion	  Science,	  38	  (1996)	  155-­‐170	  3.	  Design	  Manual	  for	  Road	  and	  Bridges,	  Waterprooﬁng	  and	  Surfacing	  on	  Concrete	  Bridge	  Decks,	  BD	  47/99	  4.	  Manual	  of	  Contract	  Documents	  for	  Highway	  Works,	  Volume	  1	  SpeciﬁcaMon	  for	  Highway	  Works	  5.	   BS	   EN	   1766:2000	   Products	   and	   systems	   for	   the	   protecMon	   and	   repair	   of	   concrete	   structures	   -­‐	   Test	   methods	   -­‐	  Reference	  concrete	  for	  tesMng	  

A Study of Aluminium Zinc Indium Thermal Spray Coatings for the Protection of Steel Rebars in Reinforced Concrete

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