TM 1-1500-204-23-9 design will be used under machine screws, countersunk fasteners,   boltheads,   and   nuts   that   would   otherwise contact magnesium. h.   Masking.  Masking of specific areas is required in painting   operations   on   large   assemblies   or   structures either   for   protective   reasons,   as   in   the   precautionary note  below,  or  for  purposes  of  delineation.    Masking conditions are as follows: NOTE Care should be taken to ensure that paint is  not  applied  to  certain  surfaces  where paint  will  interfere  with  a  function.    The following  should  be  masked  or  otherwise protected during painting: machined surfaces  that  move  with  respect  to  each other  such  as  threads,  slip  rods,  bearing contacts  and  gear  teeth;  electrical  parts, such     as     contacts,     relays,     insulators, sockets,    plugs,    connector,    wiring    and terminals; plastic and rubber (natural and synthetic)    mounts,    spacers,    etc.,    and lubrication fittings, cups, oil holes, etc. (1)    Mask  areas  such  as  windows  large  openings, etc., with combinations of barrier papers: · Military Specification MIL-B-121, usually  a  treated  paper  which  is  oil and moisture resistant. · Military Specification MIL-B-131, usually  a  laminated  toil  and  cloth  or foil  and  paper  with  good  water  vapor resistance. NOTE Both types above are heat sealable. · Crepe  backed  paper  masking  tape,  MIL- T-21595, Type I. (2)  Cover small or irregularly shaped parts with tape alone. (3)    In  repetitive  spraying  of  the  same  or  similar structures,  it  is  advisable  to  have  available  predesign bandages, socks, etc., of barrier paper or cloth. (4)    Avoid  using  tape  in  such  a  way  as  to  leave  a paint edge on surfaces unless feathering by sanding can be done safely. (5)    Use  only  approved  masking  tapes  in  varying widths required by the job.  A complex or curved area is better  masked  initially  at  the  paint  edges  with  nanow (1/2  inch)  tape.    Wider  tape  may  then  be  applied  over the narrow, if required. (6)  Use only approved masking paper for large area masking.    Coating  solvents  may  dissolve  and  deposit printing ink from newspapers, etc., on the surface of the area being masked. (7)  When spray painting, mask or cover surfaces at a   distance   from   the   area   being   painted   which   might receive overspray or paint drift. (8)    Masking  tapes  should  be  removed  as  soon  as possible after coating application. (9)    Press  tape  firmly  at  the  masking  edge  when applying it to prevent paint bleeding under it by capillary action. i.      Application   Equipment.   Application   systems   and components  of  application  equipment  are  described  in the following paragraphs. (1)  Application systems.  The application equipment plays   a   key   role   in   the   overall   success   of   painting equipment  and  components.    Selection  of  application systems and care thereafter are essential (robotics) or a manual  type.    No  description  or  details  are  provided herein because of the wide variances between equipment  manufacturers  and  local  conditions.    Each manufacturer's  instructions  and  other  details  must  be consulted.        Special    consideration    should    be    given equipment   with   which   plural   components   are   to   be applied.    Problems  may  be  encountered,  i.e.,  required accuracy  of  mixtures,  pot  life  of  mixtures  and  effects resulting  from  non-adherence  to  prescribed  application procedures. (2)      Components   of   application   equipment.      The following paragraphs describe application equipment. (a)    Automated  systems  (robots).    Such  systems include,   but   are   not   limited   to,   metering   and   mixing equipment,  air  compressors,  air  cleaners,  electrostatic generators,     spray     booths,     feed     lines     and     tanks, regulators, and computerized automated components. 9-10