What happens is that pinprick holes in the chrome plate allow in oxidants (oxygen) and the iron turns into brown iron oxide and explodes over the surface of the chrome......"rust", the hope is that the chrome is virtually intact but is covered in "rust"
Attacking the iron oxide (rust) with various chemicals (oxalate, aluminium foil) turns it back into iron which is a silver colour revealing the original chrome with the pinprick holes now a silver iron colour... The aluminium is oxidised and turns into sludge.
A level chemistry stuff
If the chrome plating is flaking you have no hope.
Its odd isnt it the way chrome rusts.
Ive just been given an orange F7 nickle plated and when i saw it i thought NO CHANCE But i found that although there seemed to be rust everywhere it cleaned off surprisingly well with clean plating under most of it.
You wouldnt think its the same fork
Polished up well with only small tell tale discolouring where the 'rust' sat.
Im autosol mental me
Mind you i have loads of parts to renovate from the bike recyclers im at.
One Shimano 105 golden arrow rear mech(short cage) in pretty poor condition.
First a smooth file to take care of the worst of the road scrapes ,then wet and dry(wet) to remove the heavy scratching left from the file. Then heavy steel wool to remove that lighter scratching(steel wool with autosol as a lube) finer steel wool@ 0000 high end German steelwool again with autosol then a soft cloth with autosol then kitchen paper to help pick up any residue and to help impart the mirror finish its now at.
Before work it was worth a tenner to the company fitted on a bike. Now its worth £35+. Im intending to collect the rest of the 105 groupset so we can sell it complete.
1976 Raleigh Chipper,1991 Muddy Fox Adventurer, 1992 Raleigh Diablo ,1992 Rudy Project, 1995 Cannondale M200 ,1997 Santa Cruz Tazmon ,1997 Specialized Stumpjumper ,1997 Specialized Rockhopper ,1997 Marin Quake 9.0,1998 Marin Pallisade trail ,1998 Raleigh Torus,1999 Orange Clockwork , 2005 Kona Hahanna , 2010 Orange Pure7
The Marvellous Mechanical Hope Collection