Root Protection Paste
Root backing paste is a special liquid applied to the underside of the part to prevent air access and scale formation during root welding. It often replaces a separate purging gas.
Physico-Chemical Mechanism of Action
The root protection paste forms a dense layer on the underside of the component, blocking air and scale. This prevents oxygen from diffusing into the metal core, which could otherwise lead to corrosion or cracking.
Metallurgical Relevance & Welding Risks
Without root protection paste, scaling and corrosion can occur on the underside of the component. This results in poor weld quality, cracks, or loss of strength. The paste also protects against air pockets and improves the formability of the metal.
Workshop Practice & Instructions
The root protection paste should be applied at least 15-20 minutes before welding. The typical paste thickness is 0.3 to 0.5 mm. Make sure the underside stays clean and dry. If the paste is missing or too thin, root welding can fail or cracks can form.