Thread lock compounds are usually manufactured in liquid and gel forms. Several manufacturers produce thread sealants. Although there are no rules about this, most manufacturers usually abide by the following color codes:
• Red. The highest strength adhesive and sealant. Usually red locking compound functions effectively at high temperatures. Powerful enough to damage some metals on removal. Use in small quantities.
• Blue. A good multipurpose adhesive and sealant rated at medium strength.
• Green. A medium strength adhesive and sealant with wicking capability; this allows it to run down threads and create a better seal.
• Purple. A low-strength thread adhesive that seals threads effectively.
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