( Corrosion ( ( is ( ( the ( gradual destruction ) ) ( of ( ( materials ( -LRB- ( usually ( metals -RRB- ) ) ) ) ( by ( ( chemical reaction ) ( with ( their environment ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Corrosion)) (VP (VBZ is) (NP (NP (DT the) (JJ gradual) (NN destruction)) (PP (IN of) (NP (NP (NP (NNS materials)) (PRN (-LRB- -LRB-) (ADVP (RB usually)) (NP (NNS metals)) (-RRB- -RRB-))) (PP (IN by) (NP (NP (NN chemical) (NN reaction)) (PP (IN with) (NP (PRP$ their) (NN environment))))))))) (. .)))
Corrosion is the gradual destruction of materials (usually metals) by chemical reaction with their environment.
(ROOT (S (NP (NP (JJ Gradual) (NN degradation)) (PP (IN of) (NP (NP (DT a) (NN material)) (ADJP (JJ due) (PP (TO to) (NP (NP (PRP$ its) (NN exposure)) (PP (TO to) (NP (DT the) (NN environment))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (NN corrosion))))) (. .)))