US 2016/0251602 Al  3  Sep. 1, 2016  [0059]  In some embodiments, the polymeric particles can  comprise foamed polymers.  [0060]  In some embodiments, the polymeric particles can  comprise unfoamed polymers.  [0061]  In some embodiments, the solid particles can be of  hollow and/or porous construction.  [0063]  In some embodiments, the non-polymeric particles  can have an average density of from about 3.5 to about 12.0  g/cm 3 •  [0062]  In some embodiments, the polymeric particles can  have an average density of from about 0.5 to about 3.5 g/cm 3 •  [0079]  In some embodiments, the one or more promoters  can comprise at least one metal chelating agent.  [0080]  In some embodiments, the one or more promoters  can comprise at least one carboxylic acid moiety.  [0081]  In some embodiments, the one or more promoters  can comprise two or more carboxylic acid moieties.  [0082]  In some embodiments, the one or more promoters  can comprise at least one citrate moiety.  [0083]  In some embodiments, the one or more promoters  can comprise at least one surfactant.  [0084]  In some embodiments, the at least one surfactant can  be a non-ionic surfactant.  [0085]  In some embodiments, the solid particles can be in  accordance with one or more of the embodiments herein› above disclosed.  [0086]  In some embodiments, the method of the treating the  metal substrate can comprise passivating the metal substrate.  [0087]  In some embodiments, the method of the treating the  metal substrate can comprise inhibiting the re-growth of an  oxide layer on the surface of the metal substrate.  [0088]  Further embodiments of the invention disclose a  metal substrate obtainable or obtained by the method of one  or more embodiments of the invention hereinabove disclosed.  [0064]  In some embodiments, the polymeric or non-poly› meric particles can have an average volume in the range of  about 5 to about 275 mm 3 •  [0065]  In some embodiments, the solid particles can be  reused one or more times for cleaning of metal substrates  according to methods of embodiments of the invention.  [0066]  In some embodiments the method can further com› prise a step of recovering the multiplicity of solid particles  after cleaning of the metal substrate. In further embodiments,  the method can comprise separating the multiplicity of solid  particles from the cleaning formulation.  [0067]  In some embodiments, the cleaning formulation can  comprise one or more components selected from the group  consisting of: solvents, polymers, corrosion inhibitors, build› ers, metal chelating agents, surfactants, dispersants, acids,  bases, anti-oxidants, reducing agents, oxidising agents and  bleaches.  [0089]  In some embodiments, the metal substrate can com› prise an oxide layer with a thickness of less than 15 nm as  measured by X-ray photoelectron spectroscopy.  [0090]  In some embodiments, the metal substrate can com› prise an oxide layer with a thickness of less than 10 nm as  measured by X-ray photoelectron spectroscopy.  [0091]  In some embodiments, the metal substrate can com› prise an oxide layer with a thickness of less than 6 nm as  measured by X-ray photoelectron spectroscopy.  [0092]  In some embodiments, the metal substrate can com› prise an oxide layer with a thickness of less than 5.4 nm as  measured by X-ray photoelectron spectroscopy.  [0093]  In some embodiments, the metal substrate can com› prise an oxide layer with a thickness of less than 3.8 nm as  measured by X-ray photoelectron spectroscopy.  [0068]  In some embodiments, the method can further com› prise coating the metal substrate after cleaning the metal  substrate. The coating can be a protective coating or lacquer.  [0069]  In some embodiments, the metal substrate can com› prise a transition metal.  [0070]  In some embodiments, the metal substrate can com› prise aluminum.  [0071]  In some embodiments, the metal substrate can be a  metal alloy.  [0072]  In some embodiments, the metal substrate can com› prise a metal sheet.  [0073]  In some embodiments, the metal substrate can be a  metal can such as an aluminum can.  [0074]  In some embodiments the method can further com› prise shaping or forming the metal substrate. Said shaping or  forming can be prior to, or subsequent to, the cleaning steps of  the method of the invention. The shaping or forming of the  substrate can be to create a final desired form of an article,  such as a can, orto form a precursor to said final desired form.  [0075]  Further embodiments of the present invention can  provide a method of treating a metal substrate. The method of  treating can comprise:  a) cleaning the metal substrate in accordance with an embodi› ment of the invention hereinabove disclosed, and  b) removing at least a portion of an oxide layer from the  surface of the cleaned substrate.  [0076]  In some embodiments, step b) can comprise expos› ing the metal substrate to a treatment liquor comprising a  treatment formulation and a multiplicity of solid particles.  [0077]  In some embodiments, step b) can further comprise  causing the solid particles and the metal substrate to enter into  contacting relative movement.  [0078]  In some embodiments, the treatment formulation  can comprise one or more promoters selected from the group  consisting of acids, bases and surfactants.  [0095]  In certain embodiments, the method of the present  invention involves cleaning a metal substrate by contacting  the substrate with a cleaning formulation and a multiplicity of  solid particles ( also referred to herein as "a solid particulate  material"). The metal substrate is contacted with the solid  particulate material such that unwanted materials and con› taminants including, but not limited to, fines (small particles  of the metal) and smut, lubricants such as oils, lubricant  residues, coolant residues, inorganic or organic salts, surfac› tants, biocides, emulsifiers and fungicides, are removed sub› stantially or completely from the surface of the substrate.  [0096]  The contact between the metal substrate and the  solid particulate material surface can comprise a mechanical  interaction and, in order to achieve this effect, contacting  relative motion can be imparted between the metal substrate  and the solid particulate material.  [0094]  FIG.  1  shows images of a pre-corroded mild steel  substrate, a pre-corroded mild steel substrate treated in accor› dance with the invention and an un-corroded mild steel sub› strate.  BRIEF DESCRIPTION OF THE DRAWING  DETAILED DESCRIPTION 