TM 1-1500-204-23-9 CAUTION Hoses should always be thoroughly cleaned    by    purging    and    flushing    with solvent appropriate to the coating material  used.    When  the  material  is  a catalytic system (epoxy or polyurethane), this  must  be  done  immediately  after  use and   before   the   prescribed   pot   life   limit has been reached to prevent the material from gelling in the system. (b) Hoses.      Because   of   friction   losses   in hose,  it  is  essential  that  the  proper  sizes  be  used.    Do not use hoses longer than 50 feet except in the case of high pressure air hoses leading to the regulator or tank. Extra  lengths  of  hose  may  be  attached  for  this  use  but should be removed when no longer needed .  The high pressure    air    hose    should    have    a    minimum    inside diameter  of  7/16  inch.    No  less  than  3/8  inch  I  D  fluid hose  should  be  used  from  the  tank  to  the  gun  and  no less than 5/16 ID air hose from the regulator to the tank and from the tank to the gun.  Any reduction in size or increase   in   length   from   the   forestated   may   produce unsatisfactory results.  Air and paint hoses are furnished in   various   standard   lengths.      Determine   the   length required for use in a spray booth measuring the width of the booth and add two feet for the total required length of the hose. (c) Spray guns for manual applications.  MIL- C-46168  paints  shall  be  applied  only  in  approved  and qualified facilities.  No application of MIL-C-46168 shall be accomplished in open air. (d) Paint  booths  and  application  equipment. No description or details is provided for painting facilities due  to  the  variance  of  equipment  and  local  conditions. For automated robotic equipment, manufacturer's instructions should be consulted. (e) Paint  brushes.    Paint  brushes  should  be used   during   touchup   procedures   in   open   air   when applying MIL-C-46168 paint.  Consult paragraph 9-3p on touchup procedures for details. j. Primers.    Primers  and  their  uses  are  described in the paragraphs that follow. (1) General use.  Primers are used on metals to  provide  a  coating  to  which  subsequent  coatings  will firmly  adhere  and  provide  protection  for  the  substrate metal against corrosion.  The pigment portion of primers for  ferrous  base  metals  usually  consists  of  iron  oxide, lead chromate, red lead, zinc chromate, zinc oxide, zinc dust, or a mixture of these.  Zinc olstrontium chromate is the   pigment   in   some   primers   used   on   substrates   of magnesium,  aluminum  and  their  alloys.    Other  primers which are lead and chromate free are desirable for most applications and required in applications where lead and zinc chromate are prohibited. (2) Use on ground support equipment. Primers   are   used   as   corrosion   inhibiting   coatings   on metal   surfaces   to   inhibit   corrosion   and   provide   good adhesion for the topcoat.  Primers will conform to MIL- P-23377 or MIL-P-85582. (3) MIL-P-23377   primer.      This   is   an   epoxy polyamide   primer   furnished   as   a   two   component   kit wherein the two components are mixed prior to use.  It is    intended    for    application    to    clean    aluminum    and magnesium  substrates.    One  component  contains  the pigment,   mixed   in   an   epoxy   vehicle,   while   the   other component consists of a clear polyamide solution which functions  as  a  hardener  for  the  epoxy  resin.    These components are packaged separately and have excellent storage stability.  When mixed, storage pot life is eight hours.  Only that amount which can be used in an eight hour period should be mixed. (4) MIL-P-85582 primer.  MIL-P-85582 primer is    a    water    reducible,    multicomponent,    epoxy    type, chemical   and   solvent   resistant   primer   coating.      The primer   is   intended   for   use   on   metal   surfaces   as   a corrosive     inhibitive,     chemical     resistant,     strippable, epoxy  primer  that  is  equivalent  to  MIL-P-23377  primer and   compatible   with   MIL-C-85285,   MIL-C-46168   and MIL-C-83286  polyurethane  topcoats.    Type  II  primer  is intended    for    use    where    low    infrared    reflectance    is required. k. Opening   of   Containers.      Containers   must   be opened  slowly  to  allow  the  pressure  to  escape  before completely removing the seal. WARNING ·   Containers     of     paint     may     develop internal   pressure   during   storage   and should be opened cautiously.  Failure to follow this procedure may result in paint being spattered in the eyes and surrounding areas. ·   Respirator    must    be    worn.        Fumes generated can cause sickness or permanent     damage     if     exposure     is prolonged. 9-11