Figure l-70. Order of Assembly for Bolted Connection
1.7.2 Surface Preparation.
Welding generally requires only the removal of foreign material which might prevent a homogeneous
weld from being established.
Before performing exothermic welding, dirt and other debris must be wiped or brushed away from the
weld area and water must be dried off before positioning the molds.
Surfaces to be brazed or soldered are to be cleaned of all foreign matter and metallic films that would
prevent adhesion of the filler metal to the primary members, and appropriate fluxes are to be applied. After
the bond has been completed, remove any excess flux or neutralizers to prevent future corrosion.
The mating surfaces of bolted and other compression type bonds require careful cleaning in accordance
with the discussion in Volume I, Section 7.6. The basic requirements are:
(1) All nonconductive material must be removed. Such materials include paints and other organic
finishes; anodize films; oxide and sulfide films; and oil, grease and other petroleum products.
(2) All corrosive agents must be removed. Such agents include water, acids, strong alkalies, and any
other materials which provide conductive electrolytic paths.
(3) All solid matter which would interfere with the establishment of a low resistance path across the
bond interface or which forms a wedge or barrier to keep the bond area open to the entrance of corrosive
materials or agents must be removed. Such solid materials include dust, dirt, sand, metal filings, and corrosion