Weldability of Steel Coated with Various Paints

Abstract

In order to investigate the weldability of mild steel coated with various paints, we made some experiments and obtained the following summaries ;
1. In manual welding (low hydrogen type and ilmenite type) and semi-automatic welding (high iron powder type), several kinds of paints, including wash primer, iron oxide, zinc chromate and new paint (oleoresinous) whose film thickness not exceeding 2 mils, had little effect on the ease of arc start, arc stability, bead appearance and on the result of the radiographic inspection.
2. Every paint film having thickness of not less than 5 mils had significant effect on the weldability of mild steel.
3. Paint films were very harmful in submerged arc welding, irrespective of kinds of paints or film thickness.
4. According to the Lehigh restraint tests, a 2-mil coat of wash primer and new paint (oleoresinous) had no effect but iron oxide and zinc chromate caused a slight rise of crack sensitivity.
5. 2-mil coat of four kinds of above-mentioned paints has no detrimental effect on V-notch Charpy impact values of deposited metals, though wash primer lowered them a little.
6. Viewing from what we stated above, we may say that wash primer, iron oxide, zinc chromate and new paint (oleoresinous) films, not exceeding a film thickness of 2 mils, have no detrimental effect on the weldability of mild steel in manual welding and semi-automatic welding.