Surface preparation

• Author: International Labour Organization
• Pages: 53-53

MEISI05-R-2005-02-0159-1-En.doc

53

8. Surface preparation

8.1. Hazard description

8.1.1. Various methods are used to remove defects, scale, oxides, and other

impurities from the surface of steel at different points in the process. These include:

(a) scarfing, which uses fixed or hand-held torches or lances to burn away the impurities;

(b) surface grinding;

(c) degreasing, which uses detergents or solvents to remove grease; and

(d) pickling, which uses acids or hydrogen peroxide to dissolve scale and oxides.

8.1.2. Each of these operations has its own hazards. Scarfing may expose workers to

metal fumes and dust, noise, and burns from scarfing lances. Alloying agents in the steel

may increase the hazard of the fumes or dust. Surface grinding also generates dust, and

involves machinery hazards. Degreasing solvents may be toxic. Acids can cause acid

burns. Degreasing and pickling of steel sheet and strip involves large tanks with coiling

machinery at each end. The coiling machinery has many nip points which need to be risk-

assessed.

8.2. Hazard control

8.2.1. Scarfing and surface grinding should be done in enclosures, with good exhaust

ventilation. Workers should be provided with respiratory protection where the ventilation

does not reduce exposure to levels below the appropriate exposure limits. Where

necessary, workers involved in scarfing should be provided with hearing protection.

8.2.2. Workers who handle pickling acids or hydrogen peroxide should be provided

with acid or chemical-resistant clothing, goggles and face shields, footwear and leggings,

and respiratory protection where necessary. Hydrofluoric acid should be handled with

extreme care, since it can cause severe poisoning in addition to acid burns.

8.2.3. To the extent practicable, acid pickling tanks and solvent degreasing tanks

should be covered, and provided with exhaust ventilation to control the vapours.

8.2.4. Care should be taken to prevent the inadvertent mixing of acids with hydrogen

peroxide or solvents. Acids should not be stored next to solvents or hydrogen peroxide.

8.2.5. Appropriate machine guarding should be provided for coiling apparatus and

other equipment used in surface preparation operations.

8.2.6. Metallic residues from surface preparation should be recycled or disposed of in

a manner that minimizes exposure to dust.